WebGPU

Editor’s Draft,

This version:
https://gpuweb.github.io/gpuweb/
Latest published version:
https://www.w3.org/TR/webgpu/
Issue Tracking:
GitHub
Inline In Spec
Editors:
(Mozilla)
(Google)
Former Editor:
(Apple)
Participate:
File an issue (open issues)

Abstract

WebGPU exposes an API for performing operations, such as rendering and computation, on a Graphics Processing Unit.

Status of this document

This specification was published by the GPU for the Web Community Group. It is not a W3C Standard nor is it on the W3C Standards Track. Please note that under the W3C Community Contributor License Agreement (CLA) there is a limited opt-out and other conditions apply. Learn more about W3C Community and Business Groups.

1. Introduction

This section is non-normative.

Graphics Processing Units, or GPUs for short, have been essential in enabling rich rendering and computational applications in personal computing. WebGPU is an API that exposes the capabilities of GPU hardware for the Web. The API is designed from the ground up to efficiently map to (post-2014) native GPU APIs. WebGPU is not related to WebGL and does not explicitly target OpenGL ES.

WebGPU sees physical GPU hardware as GPUAdapters. It provides a connection to an adapter via GPUDevice, which manages resources, and the device’s GPUQueues, which execute commands. GPUDevice may have its own memory with high-speed access to the processing units. GPUBuffer and GPUTexture are the physical resources backed by GPU memory. GPUCommandBuffer and GPURenderBundle are containers for user-recorded commands. GPUShaderModule contains shader code. The other resources, such as GPUSampler or GPUBindGroup, configure the way physical resources are used by the GPU.

GPUs execute commands encoded in GPUCommandBuffers by feeding data through a pipeline, which is a mix of fixed-function and programmable stages. Programmable stages execute shaders, which are special programs designed to run on GPU hardware. Most of the state of a pipeline is defined by a GPURenderPipeline or a GPUComputePipeline object. The state not included in these pipeline objects is set during encoding with commands, such as beginRenderPass() or setBlendConstant().

2. Malicious use considerations

This section is non-normative. It describes the risks associated with exposing this API on the Web.

2.1. Security

The security requirements for WebGPU are the same as ever for the web, and are likewise non-negotiable. The general approach is strictly validating all the commands before they reach GPU, ensuring that a page can only work with its own data.

2.1.1. CPU-based undefined behavior

A WebGPU implementation translates the workloads issued by the user into API commands specific to the target platform. Native APIs specify the valid usage for the commands (for example, see vkCreateDescriptorSetLayout) and generally don’t guarantee any outcome if the valid usage rules are not followed. This is called "undefined behavior", and it can be exploited by an attacker to access memory they don’t own, or force the driver to execute arbitrary code.

In order to disallow insecure usage, the range of allowed WebGPU behaviors is defined for any input. An implementation has to validate all the input from the user and only reach the driver with the valid workloads. This document specifies all the error conditions and handling semantics. For example, specifying the same buffer with intersecting ranges in both "source" and "destination" of copyBufferToBuffer() results in GPUCommandEncoder generating an error, and no other operation occurring.

See § 20 Errors & Debugging for more information about error handling.

2.2. GPU-based undefined behavior

WebGPU shaders are executed by the compute units inside GPU hardware. In native APIs, some of the shader instructions may result in undefined behavior on the GPU. In order to address that, the shader instruction set and its defined behaviors are strictly defined by WebGPU. When a shader is provided to createShaderModule(), the WebGPU implementation has to validate it before doing any translation (to platform-specific shaders) or transformation passes.

2.3. Uninitialized data

Generally, allocating new memory may expose the leftover data of other applications running on the system. In order to address that, WebGPU conceptually initializes all the resources to zero, although in practice an implementation may skip this step if it sees the developer initializing the contents manually. This includes variables and shared workgroup memory inside shaders.

The precise mechanism of clearing the workgroup memory can differ between platforms. If the native API does not provide facilities to clear it, the WebGPU implementation transforms the compute shader to first do a clear across all invocations, synchronize them, and continue executing developer’s code.

2.4. Out-of-bounds access in shaders

Shaders can access physical resources either directly (for example, as a "uniform" GPUBufferBinding), or via texture units, which are fixed-function hardware blocks that handle texture coordinate conversions. Validation on the API side can only guarantee that all the inputs to the shader are provided and they have the correct usage and types. The host API side can not guarantee that the data is accessed within bounds if the texture units are not involved.

define the host API distinct from the shader API

In order to prevent the shaders from accessing GPU memory an application doesn’t own, the WebGPU implementation may enable a special mode (called "robust buffer access") in the driver that guarantees that the access is limited to buffer bounds.

Alternatively, an implementation may transform the shader code by inserting manual bounds checks. When this path is taken, the out-of-bound checks only apply to array indexing. They aren’t needed for plain field access of shader structures due to the minBindingSize validation on the host side.

If the shader attempts to load data outside of physical resource bounds, the implementation is allowed to:

  1. return a value at a different location within the resource bounds

  2. return a value vector of "(0, 0, 0, X)" with any "X"

  3. partially discard the draw or dispatch call

If the shader attempts to write data outside of physical resource bounds, the implementation is allowed to:

  1. write the value to a different location within the resource bounds

  2. discard the write operation

  3. partially discard the draw or dispatch call

2.5. Invalid data

When uploading floating-point data from CPU to GPU, or generating it on the GPU, we may end up with a binary representation that doesn’t correspond to a valid number, such as infinity or NaN (not-a-number). The GPU behavior in this case is subject to the accuracy of the GPU hardware implementation of the IEEE-754 standard. WebGPU guarantees that introducing invalid floating-point numbers would only affect the results of arithmetic computations and will not have other side effects.

2.5.1. Driver bugs

GPU drivers are subject to bugs like any other software. If a bug occurs, an attacker could possibly exploit the incorrect behavior of the driver to get access to unprivileged data. In order to reduce the risk, the WebGPU working group will coordinate with GPU vendors to integrate the WebGPU Conformance Test Suite (CTS) as part of their driver testing process, like it was done for WebGL. WebGPU implementations are expected to have workarounds for some of the discovered bugs, and disable WebGPU on drivers with known bugs that can’t be worked around.

2.5.2. Timing attacks

WebGPU is designed for multi-threaded use via Web Workers. As such, it is designed not to open the users to modern high-precision timing attacks. Some of the objects, like GPUBuffer or GPUQueue, have shared state which can be simultaneously accessed. This allows race conditions to occur, similar to those of accessing a SharedArrayBuffer from multiple Web Workers, which makes the thread scheduling observable.

WebGPU addresses this by limiting the ability to deserialize (or share) objects only to the agents inside the agent cluster, and only if the cross-origin isolated policies are in place. This restriction matches the mitigations against the malicious SharedArrayBuffer use. Similarly, the user agent may also serialize the agents sharing any handles to prevent any concurrency entirely.

In the end, the attack surface for races on shared state in WebGPU will be a small subset of the SharedArrayBuffer attacks.

WebGPU also specifies the "timestamp-query" feature, which provides high precision timing of GPU operations. The feature is optional, and a WebGPU implementation may limit its exposure only to those scenarios that are trusted. Alternatively, the timing query results could be processed by a compute shader and aligned to a lower precision.

2.5.3. Row hammer attacks

Row hammer is a class of attacks that exploit the leaking of states in DRAM cells. It could be used on GPU. WebGPU does not have any specific mitigations in place, and relies on platform-level solutions, such as reduced memory refresh intervals.

2.6. Denial of service

WebGPU applications have access to GPU memory and compute units. A WebGPU implementation may limit the available GPU memory to an application, in order to keep other applications responsive. For GPU processing time, a WebGPU implementation may set up "watchdog" timer that makes sure an application doesn’t cause GPU unresponsiveness for more than a few seconds. These measures are similar to those used in WebGL.

2.7. Workload identification

WebGPU provides access to constrained global resources shared between different programs (and web pages) running on the same machine. An application can try to indirectly probe how constrained these global resources are, in order to reason about workloads performed by other open web pages, based on the patterns of usage of these shared resources. These issues are generally analogous to issues with Javascript, such as system memory and CPU execution throughput. WebGPU does not provide any additional mitigations for this.

2.7.1. Memory resources

WebGPU exposes fallible allocations from machine-global memory heaps, such as VRAM. This allows for probing the size of the system’s remaining available memory (for a given heap type) by attempting to allocate and watching for allocation failures.

GPUs internally have one or more (typically only two) heaps of memory shared by all running applications. When a heap is depleted, WebGPU would fail to create a resource. This is observable, which may allow a malicious application to guess what heaps are used by other applications, and how much they allocate from them.

2.7.2. Computation resources

If one site uses WebGPU at the same time as another, it may observe the increase in time it takes to process some work. For example, if a site constantly submits compute workloads and tracks completion of work on the queue, it may observe that something else also started using the GPU.

A GPU has many parts that can be tested independently, such as the arithmetic units, texture sampling units, atomic units, etc. A malicious application may sense when some of these units are stressed, and attempt to guess the workload of another application by analyzing the stress patterns. This is analogous to the realities of CPU execution of Javascript.

2.8. Privacy

2.8.1. Machine-specific limits

WebGPU can expose a lot of detail on the underlying GPU architecture and the device geometry. This includes available physical adapters, many limits on the GPU and CPU resources that could be used (such as the maximum texture size), and any optional hardware-specific capabilities that are available.

User agents are not obligated to expose the real hardware limits, they are in full contol of how much the machine specifics are exposed. One strategy to reduce fingerprinting is binning all the target platforms into a few number of bins. In general, the privacy impact of exposing the hardware limits matches the one of WebGL.

The default limits are also deliberately high enough to allow most application to work without requesting higher limits. All the usage of the API is validated according to the requested limits, so the actual hardware capabilities are not exposed to the users by accident.

2.8.2. Machine-specific artifacts

There are some machine-specific rasterization/precision artifacts and performance differences that can be observed roughly in the same way as in WebGL. This applies to rasterization coverage and patterns, interpolation precision of the varyings between shader stages, compute unit scheduling, and more aspects of execution.

Generally, rasterization and precision fingerprints are identical across most or all of the devices of each vendor. Performance differences are relatively intractable, but also relatively low-signal (as with JS execution performance).

Privacy-critical applications and user agents should utilize software implementations to eliminate such artifacts.

2.8.3. Machine-specific performance

Another factor for differentiating users is measuring the performance of specific operations on the GPU. Even with low precision timing, repeated execution of an operation can show if the user’s machine is fast at specific workloads. This is a fairly common vector (present in both WebGL and Javascript), but it’s also low-signal and relatively intractable to truly normalize.

WebGPU compute pipelines expose access to GPU unobstructed by the fixed-function hardware. This poses an additional risk for unique device fingerprinting. User agents can take steps to dissociate logical GPU invocations with actual compute units to reduce this risk.

2.8.4. User Agent State

This specification doesn’t define any additional user-agent state for an origin. However it is expected that user agents will have compilation caches for the result of expensive compilation like GPUShaderModule, GPURenderPipeline and GPUComputePipeline. These caches are important to improve the loading time of WebGPU applications after the first visit.

For the specification, these caches are indifferentiable from incredibly fast compilation, but for applications it would be easy to measure how long createComputePipelineAsync() takes to resolve. This can leak information across origins (like "did the user access a site with this specific shader") so user agents should follow the best practices in storage partitioning.

The system’s GPU driver may also have its own cache of compiled shaders and pipelines. User agents may want to disable these when at all possible, or add per-partition data to shaders in ways that will make the GPU driver consider them different.

3. Fundamentals

3.1. Conventions

3.1.1. Dot Syntax

In this specification, the . ("dot") syntax, common in programming languages, is used. The phrasing "Foo.Bar" means "the Bar member of the value (or interface) Foo."

The ?. ("optional chaining") syntax, adopted from JavaScript, is also used. The phrasing "Foo?.Bar" means "if Foo is null or undefined, undefined; otherwise, Foo.Bar".

For example, where buffer is a GPUBuffer, buffer?.[[device]].[[adapter]] means "if buffer is null or undefined, then undefined; otherwise, the [[adapter]] internal slot of the [[device]] internal slot of buffer.

3.1.2. Internal Objects

An internal object is a conceptual, non-exposed WebGPU object. Internal objects track the state of an API object and hold any underlying implementation. If the state of a particular internal object can change in parallel from multiple agents, those changes are always atomic with respect to all agents.

Note: An "agent" refers to a JavaScript "thread" (i.e. main thread, or Web Worker).

3.1.3. WebGPU Interfaces

A WebGPU interface is an exposed interface which encapsulates an internal object. It provides the interface through which the internal object's state is changed.

As a matter of convention, if a WebGPU interface is referred to as invalid, it means that the internal object it encapsulates is invalid.

Any interface which includes GPUObjectBase is a WebGPU interface.

interface mixin GPUObjectBase {
    attribute USVString? label;
};

GPUObjectBase has the following attributes:

label, of type USVString, nullable

A label which can be used by development tools (such as error/warning messages, browser developer tools, or platform debugging utilities) to identify the underlying internal object to the developer. It has no specified format, and therefore cannot be reliably machine-parsed.

In any given situation, the user agent may or may not choose to use this label.

GPUObjectBase has the following internal slots:

[[device]], of type device, readonly

An internal slot holding the device which owns the internal object.

3.1.4. Object Descriptors

An object descriptor holds the information needed to create an object, which is typically done via one of the create* methods of GPUDevice.

dictionary GPUObjectDescriptorBase {
    USVString label;
};

GPUObjectDescriptorBase has the following members:

label, of type USVString

The initial value of GPUObjectBase.label.

3.2. Invalid Internal Objects & Contagious Invalidity

If an object is successfully created, it is valid at that moment. An internal object may be invalid. It may become invalid during its lifetime, but it will never become valid again.

Consider separating "invalid" from "destroyed". This would let validity be immutable, and only operations involving devices, buffers, and textures (e.g. submit, map) would check those objects' [[destroyed]] state (explicitly).

Invalid objects result from a number of situations, including:
To determine if a given GPUObjectBase object is valid to use with a targetObject, run the following steps:
  1. If any of the following conditions are unsatisfied return false:

  2. Return true.

3.3. Coordinate Systems

Note: WebGPU’s coordinate systems match DirectX’s coordinate systems in a graphics pipeline.

3.4. Programming Model

3.4.1. Timelines

This section is non-normative.

A computer system with a user agent at the front-end and GPU at the back-end has components working on different timelines in parallel:

Content timeline

Associated with the execution of the Web script. It includes calling all methods described by this specification.

Steps executed on the content timeline look like this.
Device timeline

Associated with the GPU device operations that are issued by the user agent. It includes creation of adapters, devices, and GPU resources and state objects, which are typically synchronous operations from the point of view of the user agent part that controls the GPU, but can live in a separate OS process.

Steps executed on the device timeline look like this.
Queue timeline

Associated with the execution of operations on the compute units of the GPU. It includes actual draw, copy, and compute jobs that run on the GPU.

Steps executed on the queue timeline look like this.

In this specification, asynchronous operations are used when the result value depends on work that happens on any timeline other than the Content timeline. They are represented by callbacks and promises in JavaScript.

GPUComputePassEncoder.dispatch():
  1. User encodes a dispatch command by calling a method of the GPUComputePassEncoder which happens on the Content timeline.

  2. User issues GPUQueue.submit() that hands over the GPUCommandBuffer to the user agent, which processes it on the Device timeline by calling the OS driver to do a low-level submission.

  3. The submit gets dispatched by the GPU invocation scheduler onto the actual compute units for execution, which happens on the Queue timeline.

GPUDevice.createBuffer():
  1. User fills out a GPUBufferDescriptor and creates a GPUBuffer with it, which happens on the Content timeline.

  2. User agent creates a low-level buffer on the Device timeline.

GPUBuffer.mapAsync():
  1. User requests to map a GPUBuffer on the Content timeline and gets a promise in return.

  2. User agent checks if the buffer is currently used by the GPU and makes a reminder to itself to check back when this usage is over.

  3. After the GPU operating on Queue timeline is done using the buffer, the user agent maps it to memory and resolves the promise.

3.4.2. Memory Model

This section is non-normative.

Once a GPUDevice has been obtained during an application initialization routine, we can describe the WebGPU platform as consisting of the following layers:

  1. User agent implementing the specification.

  2. Operating system with low-level native API drivers for this device.

  3. Actual CPU and GPU hardware.

Each layer of the WebGPU platform may have different memory types that the user agent needs to consider when implementing the specification:

Most physical resources are allocated in the memory of type that is efficient for computation or rendering by the GPU. When the user needs to provide new data to the GPU, the data may first need to cross the process boundary in order to reach the user agent part that communicates with the GPU driver. Then it may need to be made visible to the driver, which sometimes requires a copy into driver-allocated staging memory. Finally, it may need to be transferred to the dedicated GPU memory, potentially changing the internal layout into one that is most efficient for GPUs to operate on.

All of these transitions are done by the WebGPU implementation of the user agent.

Note: This example describes the worst case, while in practice the implementation may not need to cross the process boundary, or may be able to expose the driver-managed memory directly to the user behind an ArrayBuffer, thus avoiding any data copies.

3.4.3. Multi-Threading

3.4.4. Resource Usages

A physical resource can be used on GPU with an internal usage:

input

Buffer with input data for draw or dispatch calls. Preserves the contents. Allowed by buffer INDEX, buffer VERTEX, or buffer INDIRECT.

constant

Resource bindings that are constant from the shader point of view. Preserves the contents. Allowed by buffer UNIFORM or texture TEXTURE_BINDING.

storage

Writable storage resource binding. Allowed by buffer STORAGE or texture STORAGE_BINDING.

storage-read

Read-only storage resource bindings. Preserves the contents. Allowed by buffer STORAGE.

attachment

Texture used as an output attachment in a render pass. Allowed by texture RENDER_ATTACHMENT.

attachment-read

Texture used as a read-only attachment in a render pass. Preserves the contents. Allowed by texture RENDER_ATTACHMENT.

Textures may consist of separate mipmap levels and array layers, which can be used differently at any given time. Each such texture subresource is uniquely identified by a texture, mipmap level, and (for 2d textures only) array layer, and aspect.

We define subresource to be either a whole buffer, or a texture subresource.

Some internal usages are compatible with others. A subresource can be in a state that combines multiple usages together. We consider a list U to be a compatible usage list if (and only if) it satisfies any of the following rules:

Enforcing that the usages are only combined into a compatible usage list allows the API to limit when data races can occur in working with memory. That property makes applications written against WebGPU more likely to run without modification on different platforms.

Generally, when an implementation processes an operation that uses a subresource in a different way than its current usage allows, it schedules a transition of the resource into the new state. In some cases, like within an open GPURenderPassEncoder, such a transition is impossible due to the hardware limitations. We define these places as usage scopes.

The main usage rule is, for any one subresource, its list of internal usages within one usage scope must be a compatible usage list.

For example, binding the same buffer for storage as well as for input within the same GPURenderPassEncoder would put the encoder as well as the owning GPUCommandEncoder into the error state. This combination of usages does not make a compatible usage list.

Note: race condition of multiple writable storage buffer/texture usages in a single usage scope is allowed.

The subresources of textures included in the views provided to GPURenderPassColorAttachment.view and GPURenderPassColorAttachment.resolveTarget are considered to be used as attachment for the usage scope of this render pass.

The physical size of a texture subresource is the dimension of the texture subresource in texels that includes the possible extra paddings to form complete texel blocks in the subresource.

Considering a GPUTexture in BC format whose [[descriptor]].size is {60, 60, 1}, when sampling the GPUTexture at mipmap level 2, the sampling hardware uses {15, 15, 1} as the size of the texture subresource, while its physical size is {16, 16, 1} as the block-compression algorithm can only operate on 4x4 texel blocks.

3.4.5. Synchronization

For each subresource of a physical resource, its set of internal usage flags is tracked on the Queue timeline.

This section will need to be revised to support multiple queues.

On the Queue timeline, there is an ordered sequence of usage scopes. For the duration of each scope, the set of internal usage flags of any given subresource is constant. A subresource may transition to new usages at the boundaries between usage scopes.

This specification defines the following usage scopes:

The above should probably talk about GPU commands. But we don’t have a way to reference specific GPU commands (like dispatch) yet.

The above rules mean the following example resource usages are included in usage scope validation:

During command encoding, every usage of a subresource is recorded in one of the usage scopes in the command buffer. For each usage scope, the implementation performs usage scope validation by composing the list of all internal usage flags of each subresource used in the usage scope. If any of those lists is not a compatible usage list, GPUCommandEncoder.finish() generates a GPUValidationError in the current error scope.

3.5. Core Internal Objects

3.5.1. Adapters

An adapter represents an implementation of WebGPU on the system. Each adapter identifies both an instance of compute/rendering functionality on a platform underlying a browser, and an instance of a browser’s implementation of WebGPU on top of that functionality.

If an adapter becomes unavailable, it becomes invalid. Once invalid, it never becomes valid again. Any devices on the adapter, and internal objects owned by those devices, also become invalid.

Note: An adapter may be a physical display adapter (GPU), but it could also be a software renderer. A returned adapter could refer to different physical adapters, or to different browser codepaths or system drivers on the same physical adapters. Applications can hold onto multiple adapters at once (via GPUAdapter) (even if some are invalid), and two of these could refer to different instances of the same physical configuration (e.g. if the GPU was reset or disconnected and reconnected).

An adapter may be considered a fallback adapter if it has significant performance caveats in exchange for some combination of wider compatibility, more predictable behavior, or improved privacy. It is not required that a fallback adapter is available on every system.

An adapter has the following internal slots:

[[features]], of type ordered set<GPUFeatureName>, readonly

The features which can be used to create devices on this adapter.

[[limits]], of type supported limits, readonly

The best limits which can be used to create devices on this adapter.

Each adapter limit must be the same or better than its default value in supported limits.

[[current]], of type boolean

Indicates whether the adapter is allowed to vend new devices at this time. Its value may change at any time.

It is initially set to true inside requestAdapter(). It becomes false inside "lose the device" and "mark adapters stale". Once set to false, it cannot become true again.

Note: This mechanism ensures that various adapter-creation scenarios look similar to applications, so they can easily be robust to more scenarios with less testing: first initialization, reinitialization due to an unplugged adapter, reinitialization due to a test GPUDevice.destroy() call, etc. It also ensures applications use the latest system state to make decisions about which adapter to use.

[[fallback]], of type boolean

If set to true indicates that the adapter is a fallback adapter.

Adapters are exposed via GPUAdapter.

3.5.2. Devices

A device is the logical instantiation of an adapter, through which internal objects are created. It can be shared across multiple agents (e.g. dedicated workers).

A device is the exclusive owner of all internal objects created from it: when the device is lost, it and all objects created on it (directly, e.g. createTexture(), or indirectly, e.g. createView()) become invalid.

Define "ownership".

A device has the following internal slots:

[[adapter]], of type adapter, readonly

The adapter from which this device was created.

[[features]], of type ordered set<GPUFeatureName>, readonly

The features which can be used on this device. No additional features can be used, even if the underlying adapter can support them.

[[limits]], of type supported limits, readonly

The limits which can be used on this device. No better limits can be used, even if the underlying adapter can support them.

When a new device device is created from adapter adapter with GPUDeviceDescriptor descriptor:

Any time the user agent needs to revoke access to a device, it calls lose the device(device, undefined).

To lose the device(device, reason):
  1. Set device.[[adapter]].[[current]] to false.

  2. explain how to get from device to its "primary" GPUDevice.

  3. Resolve GPUDevice.lost with a new GPUDeviceLostInfo with reason set to reason and message set to an implementation-defined value.

    Note: message should not disclose unnecessary user/system information and should never be parsed by applications.

Devices are exposed via GPUDevice.

3.6. Optional Capabilities

WebGPU adapters and devices have capabilities, which describe WebGPU functionality that differs between different implementations, typically due to hardware or system software constraints. A capability is either a feature or a limit.

3.6.1. Features

A feature is a set of optional WebGPU functionality that is not supported on all implementations, typically due to hardware or system software constraints.

Each GPUAdapter exposes a set of available features. Only those features may be requested in requestDevice().

Functionality that is part of an feature may only be used if the feature was requested at device creation. See the Feature Index for a description of the functionality each feature enables.

3.6.2. Limits

Each limit is a numeric limit on the usage of WebGPU on a device.

A supported limits object has a value for every defined limit. Each adapter has a set of supported limits, and devices are created with specific supported limits in place. The device limits are enforced regardless of the adapter’s limits.

One limit value may be better than another. A better limit value always relaxes validation, enabling strictly more programs to be valid. For each limit, "better" is defined.

Note: Setting "better" limits may not necessarily be desirable, as they may have a performance impact. Because of this, and to improve portability across devices and implementations, applications should generally request the "worst" limits that work for their content (ideally, the default values).

Each limit also has a default value. Every adapter is guaranteed to support the default value or better. The default is used if a value is not explicitly specified in requiredLimits.

Limit name Type Better Default
maxTextureDimension1D GPUSize32 Higher 8192
The maximum allowed value for the size.width of a texture created with dimension "1d".
maxTextureDimension2D GPUSize32 Higher 8192
The maximum allowed value for the size.width and size.height of a texture created with dimension "2d".
maxTextureDimension3D GPUSize32 Higher 2048
The maximum allowed value for the size.width, size.height and size.depthOrArrayLayers of a texture created with dimension "3d".
maxTextureArrayLayers GPUSize32 Higher 256
The maximum allowed value for the size.depthOrArrayLayers of a texture created with dimension "1d" or "2d".
maxBindGroups GPUSize32 Higher 4
The maximum number of GPUBindGroupLayouts allowed in bindGroupLayouts when creating a GPUPipelineLayout.
maxDynamicUniformBuffersPerPipelineLayout GPUSize32 Higher 8
The maximum number of GPUBindGroupLayoutEntry entries across a GPUPipelineLayout which are uniform buffers with dynamic offsets. See Exceeds the binding slot limits.
maxDynamicStorageBuffersPerPipelineLayout GPUSize32 Higher 4
The maximum number of GPUBindGroupLayoutEntry entries across a GPUPipelineLayout which are storage buffers with dynamic offsets. See Exceeds the binding slot limits.
maxSampledTexturesPerShaderStage GPUSize32 Higher 16
For each possible GPUShaderStage stage, the maximum number of GPUBindGroupLayoutEntry entries across a GPUPipelineLayout which are sampled textures. See Exceeds the binding slot limits.
maxSamplersPerShaderStage GPUSize32 Higher 16
For each possible GPUShaderStage stage, the maximum number of GPUBindGroupLayoutEntry entries across a GPUPipelineLayout which are samplers. See Exceeds the binding slot limits.
maxStorageBuffersPerShaderStage GPUSize32 Higher 8
For each possible GPUShaderStage stage, the maximum number of GPUBindGroupLayoutEntry entries across a GPUPipelineLayout which are storage buffers. See Exceeds the binding slot limits.
maxStorageTexturesPerShaderStage GPUSize32 Higher 4
For each possible GPUShaderStage stage, the maximum number of GPUBindGroupLayoutEntry entries across a GPUPipelineLayout which are storage textures. See Exceeds the binding slot limits.
maxUniformBuffersPerShaderStage GPUSize32 Higher 12
For each possible GPUShaderStage stage, the maximum number of GPUBindGroupLayoutEntry entries across a GPUPipelineLayout which are uniform buffers. See Exceeds the binding slot limits.
maxUniformBufferBindingSize GPUSize64 Higher 16384
The maximum GPUBufferBinding.size for bindings with a GPUBindGroupLayoutEntry entry for which entry.buffer?.type is "uniform".
maxStorageBufferBindingSize GPUSize64 Higher 134217728 (128 MiB)
The maximum GPUBufferBinding.size for bindings with a GPUBindGroupLayoutEntry entry for which entry.buffer?.type is "storage" or "read-only-storage".
minUniformBufferOffsetAlignment GPUSize32 Lower 256
The required alignment for GPUBufferBinding.offset and setBindGroup dynamicOffsets arguments for binding with a GPUBindGroupLayoutEntry entry for which entry.buffer?.type is "uniform".
minStorageBufferOffsetAlignment GPUSize32 Lower 256
The required alignment for GPUBufferBinding.offset and setBindGroup dynamicOffsets arguments for binding with a GPUBindGroupLayoutEntry entry for which entry.buffer?.type is "storage" or "read-only-storage".
maxVertexBuffers GPUSize32 Higher 8
The maximum number of buffers when creating a GPURenderPipeline.
maxVertexAttributes GPUSize32 Higher 16
The maximum number of attributes in total across buffers when creating a GPURenderPipeline.
maxVertexBufferArrayStride GPUSize32 Higher 2048
The maximum allowed arrayStride when creating a GPURenderPipeline.
maxInterStageShaderComponents GPUSize32 Higher 60
The maximum allowed number of components of input or output variables for inter-stage communication (like vertex outputs or fragment inputs).
maxComputeWorkgroupStorageSize GPUSize32 Higher 16352
The maximum number of bytes used for a compute stage GPUShaderModule entry-point.
maxComputeInvocationsPerWorkgroup GPUSize32 Higher 256
The maximum value of the product of the workgroup_size dimensions for a compute stage GPUShaderModule entry-point.
maxComputeWorkgroupSizeX GPUSize32 Higher 256
The maximum value of the workgroup_size X dimension for a compute stage GPUShaderModule entry-point.
maxComputeWorkgroupSizeY GPUSize32 Higher 256
The maximum value of the workgroup_size Y dimensions for a compute stage GPUShaderModule entry-point.
maxComputeWorkgroupSizeZ GPUSize32 Higher 64
The maximum value of the workgroup_size Z dimensions for a compute stage GPUShaderModule entry-point.
maxComputeWorkgroupsPerDimension GPUSize32 Higher 65535
The maximum value for the arguments of dispatch(x, y, z).

Do we need to have a max per-pixel render target size?

3.6.2.1. GPUSupportedLimits

GPUSupportedLimits exposes the limits supported by an adapter or device. See GPUAdapter.limits and GPUDevice.limits.

[Exposed=(Window, DedicatedWorker)]
interface GPUSupportedLimits {
    readonly attribute unsigned long maxTextureDimension1D;
    readonly attribute unsigned long maxTextureDimension2D;
    readonly attribute unsigned long maxTextureDimension3D;
    readonly attribute unsigned long maxTextureArrayLayers;
    readonly attribute unsigned long maxBindGroups;
    readonly attribute unsigned long maxDynamicUniformBuffersPerPipelineLayout;
    readonly attribute unsigned long maxDynamicStorageBuffersPerPipelineLayout;
    readonly attribute unsigned long maxSampledTexturesPerShaderStage;
    readonly attribute unsigned long maxSamplersPerShaderStage;
    readonly attribute unsigned long maxStorageBuffersPerShaderStage;
    readonly attribute unsigned long maxStorageTexturesPerShaderStage;
    readonly attribute unsigned long maxUniformBuffersPerShaderStage;
    readonly attribute unsigned long long maxUniformBufferBindingSize;
    readonly attribute unsigned long long maxStorageBufferBindingSize;
    readonly attribute unsigned long minUniformBufferOffsetAlignment;
    readonly attribute unsigned long minStorageBufferOffsetAlignment;
    readonly attribute unsigned long maxVertexBuffers;
    readonly attribute unsigned long maxVertexAttributes;
    readonly attribute unsigned long maxVertexBufferArrayStride;
    readonly attribute unsigned long maxInterStageShaderComponents;
    readonly attribute unsigned long maxComputeWorkgroupStorageSize;
    readonly attribute unsigned long maxComputeInvocationsPerWorkgroup;
    readonly attribute unsigned long maxComputeWorkgroupSizeX;
    readonly attribute unsigned long maxComputeWorkgroupSizeY;
    readonly attribute unsigned long maxComputeWorkgroupSizeZ;
    readonly attribute unsigned long maxComputeWorkgroupsPerDimension;
};
3.6.2.2. GPUSupportedFeatures

GPUSupportedFeatures is a setlike interface. Its set entries are the GPUFeatureName values of the features supported by an adapter or device. It must only contain strings from the GPUFeatureName enum.

[Exposed=(Window, DedicatedWorker)]
interface GPUSupportedFeatures {
    readonly setlike<DOMString>;
};
Note: The type of the GPUSupportedFeatures set entries is DOMString to allow user agents to gracefully handle valid GPUFeatureNames which are added in later revisions of the spec but which the user agent has not been updated to recognize yet. If the set entries type was GPUFeatureName the following code would throw an TypeError rather than reporting false:
Check for support of an unrecognized feature:
if (adapter.features.has('unknown-feature')) {
    // Use unknown-feature
} else {
    console.warn('unknown-feature is not supported by this adapter.');
}

3.7. Origin Restrictions

WebGPU allows accessing image data stored in images, videos, and canvases. Restrictions are imposed on the use of cross-domain media, because shaders can be used to indirectly deduce the contents of textures which have been uploaded to the GPU.

WebGPU disallows uploading an image source if it is not origin-clean.

This also implies that the origin-clean flag for a canvas rendered using WebGPU will never be set to false.

For more information on issuing CORS requests for image and video elements, consult:

3.8. Color Spaces and Encoding

WebGPU does not provide color management. All values within WebGPU (such as texture elements) are raw numeric values, not color-managed color values.

WebGPU does interface with color-managed outputs (via GPUCanvasConfiguration) and inputs (via copyExternalImageToTexture() and importExternalTexture()). Color conversion must be performed between the WebGPU numeric values and the external color values. Each such interface point locally defines an encoding (color space, transfer function, and alpha premultiplication) in which the WebGPU numeric values are to be interpreted.

enum GPUPredefinedColorSpace {
    "srgb",
};

Possibly replace this with PredefinedColorSpace, but note that doing so would mean new WebGPU functionality gets added automatically when items are added to that enum in the upstream spec.

Consider a path for uploading srgb-encoded images into linearly-encoded textures. [Issue #gpuweb/gpuweb#1715]

"srgb"

The CSS predefined color space srgb.

4. Initialization

4.1. Examples

Need a robust example like the one in ErrorHandling.md, which handles all situations. Possibly also include a simple example with no handling.

A GPU object is available in the Window and DedicatedWorkerGlobalScope contexts through the Navigator and WorkerNavigator interfaces respectively and is exposed via navigator.gpu:

interface mixin NavigatorGPU {
    [SameObject, SecureContext] readonly attribute GPU gpu;
};
Navigator includes NavigatorGPU;
WorkerNavigator includes NavigatorGPU;

4.3. GPU

GPU is the entry point to WebGPU.

[Exposed=(Window, DedicatedWorker), SecureContext]
interface GPU {
    Promise<GPUAdapter?> requestAdapter(optional GPURequestAdapterOptions options = {});
};

GPU has the following methods:

requestAdapter(options)

Requests an adapter from the user agent. The user agent chooses whether to return an adapter, and, if so, chooses according to the provided options.

Called on: GPU this.

Arguments:

Arguments for the GPU.requestAdapter(options) method.
Parameter Type Nullable Optional Description
options GPURequestAdapterOptions Criteria used to select the adapter.

Returns: Promise<GPUAdapter?>

  1. Let promise be a new promise.

  2. Issue the following steps on the Device timeline of this:

    1. If the user agent chooses to return an adapter, it should:

      1. Create an adapter adapter with [[current]] set to true, chosen according to the rules in § 4.3.1 Adapter Selection and the criteria in options.

      2. If adapter meets the criteria of a fallback adapter set adapter.[[fallback]] to true.

      3. Resolve promise with a new GPUAdapter encapsulating adapter.

    2. Otherwise, promise resolves with null.

  3. Return promise.

GPU has the following internal slots:

[[previously_returned_adapters]], of type ordered set<adapter>

The set of adapters that have been returned via requestAdapter(). It is used, then cleared, in mark adapters stale.

Upon any change in the system’s state that could affect the result of any requestAdapter() call, the user agent should mark adapters stale. For example:

Additionally, mark adapters stale may by scheduled at any time. User agents may choose to do this often even when there has been no system state change (e.g. several seconds after the last call to requestDevice(). This has no effect on well-formed applications, obfuscates real system state changes, and makes developers more aware that calling requestAdapter() again is always necessary before calling requestDevice().

To mark adapters stale:
  1. For each adapter in navigator.gpu.[[previously_returned_adapters]]:

    1. Set adapter.[[adapter]].[[current]] to false.

  2. Empty navigator.gpu.[[previously_returned_adapters]].

Update here if an adaptersadded/adapterschanged event is introduced.

Request a GPUAdapter:
const adapter = await navigator.gpu.requestAdapter(/* ... */);
const features = adapter.features;
// ...

4.3.1. Adapter Selection

GPURequestAdapterOptions provides hints to the user agent indicating what configuration is suitable for the application.

dictionary GPURequestAdapterOptions {
    GPUPowerPreference powerPreference;
    boolean forceFallbackAdapter = false;
};
enum GPUPowerPreference {
    "low-power",
    "high-performance"
};

GPURequestAdapterOptions has the following members:

powerPreference, of type GPUPowerPreference

Optionally provides a hint indicating what class of adapter should be selected from the system’s available adapters.

The value of this hint may influence which adapter is chosen, but it must not influence whether an adapter is returned or not.

Note: The primary utility of this hint is to influence which GPU is used in a multi-GPU system. For instance, some laptops have a low-power integrated GPU and a high-performance discrete GPU.

Note: Depending on the exact hardware configuration, such as battery status and attached displays or removable GPUs, the user agent may select different adapters given the same power preference. Typically, given the same hardware configuration and state and powerPreference, the user agent is likely to select the same adapter.

It must be one of the following values:

undefined (or not present)

Provides no hint to the user agent.

"low-power"

Indicates a request to prioritize power savings over performance.

Note: Generally, content should use this if it is unlikely to be constrained by drawing performance; for example, if it renders only one frame per second, draws only relatively simple geometry with simple shaders, or uses a small HTML canvas element. Developers are encouraged to use this value if their content allows, since it may significantly improve battery life on portable devices.

"high-performance"

Indicates a request to prioritize performance over power consumption.

Note: By choosing this value, developers should be aware that, for devices created on the resulting adapter, user agents are more likely to force device loss, in order to save power by switching to a lower-power adapter. Developers are encouraged to only specify this value if they believe it is absolutely necessary, since it may significantly decrease battery life on portable devices.

forceFallbackAdapter, of type boolean, defaulting to false

When set to true indicates that only a fallback adapter may be returned. If the user agent does not support a fallback adapter, will cause requestAdapter() to resolve to null.

Note: requestAdapter() may still return a fallback adapter if forceFallbackAdapter is set to false and either no other appropriate adapter is available or the user agent chooses to return a fallback adapter. Developers that wish to prevent their applications from running on fallback adapters should check the GPUAdapter.isFallbackAdapter attribute prior to requesting a GPUDevice.

4.4. GPUAdapter

A GPUAdapter encapsulates an adapter, and describes its capabilities (features and limits).

To get a GPUAdapter, use requestAdapter().

[Exposed=(Window, DedicatedWorker), SecureContext]
interface GPUAdapter {
    readonly attribute DOMString name;
    [SameObject] readonly attribute GPUSupportedFeatures features;
    [SameObject] readonly attribute GPUSupportedLimits limits;
    readonly attribute boolean isFallbackAdapter;

    Promise<GPUDevice> requestDevice(optional GPUDeviceDescriptor descriptor = {});
};

GPUAdapter has the following attributes:

name, of type DOMString, readonly

A human-readable name identifying the adapter. The contents are implementation-defined.

features, of type GPUSupportedFeatures, readonly

The set of values in this.[[adapter]].[[features]].

limits, of type GPUSupportedLimits, readonly

The limits in this.[[adapter]].[[limits]].

isFallbackAdapter, of type boolean, readonly

Returns the value of [[adapter]].[[fallback]].

GPUAdapter has the following internal slots:

[[adapter]], of type adapter, readonly

The adapter to which this GPUAdapter refers.

GPUAdapter has the following methods:

requestDevice(descriptor)

Requests a device from the adapter.

Called on: GPUAdapter this.

Arguments:

Arguments for the GPUAdapter.requestDevice(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUDeviceDescriptor Description of the GPUDevice to request.

Returns: Promise<GPUDevice?>

  1. Let promise be a new promise.

  2. Let adapter be this.[[adapter]].

  3. Issue the following steps to the Device timeline:

    1. If any of the following requirements are unmet, reject promise with a TypeError and stop.

    2. If any of the following requirements are unmet, reject promise with an OperationError and stop.

    3. If adapter.[[current]] is false, or the user agent otherwise cannot fulfill the request:

      1. Let device be a new device.

      2. Lose the device(device, undefined).

        Note: This makes adapter.[[current]] false, if it wasn’t already.

        Note: User agents should consider issuing developer-visible warnings in most or all cases when this occurs. Applications should perform reinitialization logic starting with requestAdapter().

      3. Resolve promise with a new GPUDevice encapsulating device, and stop.

    4. Resolve promise with a new GPUDevice object encapsulating a new device with the capabilities described by descriptor.

  4. Return promise.

4.4.1. GPUDeviceDescriptor

GPUDeviceDescriptor describes a device request.

dictionary GPUDeviceDescriptor : GPUObjectDescriptorBase {
    sequence<GPUFeatureName> requiredFeatures = [];
    record<DOMString, GPUSize64> requiredLimits = {};
};

GPUDeviceDescriptor has the following members:

requiredFeatures, of type sequence<GPUFeatureName>, defaulting to []

Specifies the features that are required by the device request. The request will fail if the adapter cannot provide these features.

Exactly the specified set of features, and no more or less, will be allowed in validation of API calls on the resulting device.

requiredLimits, of type record<DOMString, GPUSize64>, defaulting to {}

Specifies the limits that are required by the device request. The request will fail if the adapter cannot provide these limits.

Each key must be the name of a member of supported limits. Exactly the specified limits, and no better or worse, will be allowed in validation of API calls on the resulting device.

4.4.1.1. GPUFeatureName

Each GPUFeatureName identifies a set of functionality which, if available, allows additional usages of WebGPU that would have otherwise been invalid.

enum GPUFeatureName {
    "depth-clamping",
    "depth24unorm-stencil8",
    "depth32float-stencil8",
    "pipeline-statistics-query",
    "texture-compression-bc",
    "texture-compression-etc2",
    "texture-compression-astc",
    "timestamp-query",
};

4.5. GPUDevice

A GPUDevice encapsulates a device and exposes the functionality of that device.

GPUDevice is the top-level interface through which WebGPU interfaces are created.

To get a GPUDevice, use requestDevice().

[Exposed=(Window, DedicatedWorker), SecureContext]
interface GPUDevice : EventTarget {
    [SameObject] readonly attribute GPUSupportedFeatures features;
    [SameObject] readonly attribute GPUSupportedLimits limits;

    [SameObject] readonly attribute GPUQueue queue;

    undefined destroy();

    GPUBuffer createBuffer(GPUBufferDescriptor descriptor);
    GPUTexture createTexture(GPUTextureDescriptor descriptor);
    GPUSampler createSampler(optional GPUSamplerDescriptor descriptor = {});
    GPUExternalTexture importExternalTexture(GPUExternalTextureDescriptor descriptor);

    GPUBindGroupLayout createBindGroupLayout(GPUBindGroupLayoutDescriptor descriptor);
    GPUPipelineLayout createPipelineLayout(GPUPipelineLayoutDescriptor descriptor);
    GPUBindGroup createBindGroup(GPUBindGroupDescriptor descriptor);

    GPUShaderModule createShaderModule(GPUShaderModuleDescriptor descriptor);
    GPUComputePipeline createComputePipeline(GPUComputePipelineDescriptor descriptor);
    GPURenderPipeline createRenderPipeline(GPURenderPipelineDescriptor descriptor);
    Promise<GPUComputePipeline> createComputePipelineAsync(GPUComputePipelineDescriptor descriptor);
    Promise<GPURenderPipeline> createRenderPipelineAsync(GPURenderPipelineDescriptor descriptor);

    GPUCommandEncoder createCommandEncoder(optional GPUCommandEncoderDescriptor descriptor = {});
    GPURenderBundleEncoder createRenderBundleEncoder(GPURenderBundleEncoderDescriptor descriptor);

    GPUQuerySet createQuerySet(GPUQuerySetDescriptor descriptor);
};
GPUDevice includes GPUObjectBase;

GPUDevice has the following attributes:

features, of type GPUSupportedFeatures, readonly

A set containing the GPUFeatureName values of the features supported by the device (i.e. the ones with which it was created).

limits, of type GPUSupportedLimits, readonly

Exposes the limits supported by the device (which are exactly the ones with which it was created).

queue, of type GPUQueue, readonly

The primary GPUQueue for this device.

The [[device]] for a GPUDevice is the device that the GPUDevice refers to.

GPUDevice has the methods listed in its WebIDL definition above. Those not defined here are defined elsewhere in this document.

destroy()

Destroys the device, preventing further operations on it. Outstanding asynchronous operations will fail.

Called on: GPUDevice this.
  1. Lose the device(this.[[device]], "destroyed").

Note: Since no further operations can occur on this device, implementations can free resource allocations and abort outstanding asynchronous operations immediately.

GPUDevice objects are serializable objects.

Finish defining multithreading API and add [Serializable] back to the interface. [Issue #gpuweb/gpuweb#354]

The steps to serialize a GPUDevice object, given value, serialized, and forStorage, are:
  1. Set serialized.agentCluster to be the surrounding agent's agent cluster.

  2. If serialized.agentCluster’s cross-origin isolated capability is false, throw a "DataCloneError".

  3. If forStorage is true, throw a "DataCloneError".

  4. Set serialized.device to the value of value.[[device]].

The steps to deserialize a GPUDevice object, given serialized and value, are:
  1. If serialized.agentCluster is not the surrounding agent's agent cluster, throw a "DataCloneError".

  2. Set value.[[device]] to serialized.device.

GPUDevice doesn’t really need the cross-origin policy restriction. It should be usable from multiple agents regardless. Once we describe the serialization of buffers, textures, and queues - the COOP+COEP logic should be moved in there.

5. Buffers

5.1. GPUBuffer

define buffer (internal object)

A GPUBuffer represents a block of memory that can be used in GPU operations. Data is stored in linear layout, meaning that each byte of the allocation can be addressed by its offset from the start of the GPUBuffer, subject to alignment restrictions depending on the operation. Some GPUBuffers can be mapped which makes the block of memory accessible via an ArrayBuffer called its mapping.

GPUBuffers are created via GPUDevice.createBuffer(descriptor) that returns a new buffer in the mapped or unmapped state.

[Exposed=(Window, DedicatedWorker), SecureContext]
interface GPUBuffer {
    Promise<undefined> mapAsync(GPUMapModeFlags mode, optional GPUSize64 offset = 0, optional GPUSize64 size);
    ArrayBuffer getMappedRange(optional GPUSize64 offset = 0, optional GPUSize64 size);
    undefined unmap();

    undefined destroy();
};
GPUBuffer includes GPUObjectBase;

GPUBuffer has the following internal slots:

[[size]] of type GPUSize64.

The length of the GPUBuffer allocation in bytes.

[[usage]] of type GPUBufferUsageFlags.

The allowed usages for this GPUBuffer.

[[state]] of type buffer state.

The current state of the GPUBuffer.

[[mapping]] of type ArrayBuffer or Promise or null.

The mapping for this GPUBuffer. The ArrayBuffer isn’t directly accessible and is instead accessed through views into it, called the mapped ranges, that are stored in [[mapped_ranges]]

Specify [[mapping]] in term of DataBlock similarly to AllocateArrayBuffer? [Issue #gpuweb/gpuweb#605]

[[mapping_range]] of type list<unsigned long long> or null.

The range of this GPUBuffer that is mapped.

[[mapped_ranges]] of type list<ArrayBuffer> or null.

The ArrayBuffers returned via getMappedRange to the application. They are tracked so they can be detached when unmap is called.

[[map_mode]] of type GPUMapModeFlags.

The GPUMapModeFlags of the last call to mapAsync() (if any).

[[usage]] is differently named from [[descriptor]].usage. We should make it consistent.

Each GPUBuffer has a current buffer state on the Content timeline which is one of the following:

Note: [[size]] and [[usage]] are immutable once the GPUBuffer has been created.

Note: GPUBuffer has a state machine with the following states. ([[mapping]], [[mapping_range]], and [[mapped_ranges]] are null when not specified.)

GPUBuffer is Serializable. It is a reference to an internal buffer object, and Serializable means that the reference can be copied between realms (threads/workers), allowing multiple realms to access it concurrently. Since GPUBuffer has internal state (mapped, destroyed), that state is internally-synchronized - these state changes occur atomically across realms.

Finish defining multithreading API and add [Serializable] back to the interface. [Issue #gpuweb/gpuweb#354]

5.2. Buffer Creation

5.2.1. GPUBufferDescriptor

This specifies the options to use in creating a GPUBuffer.

dictionary GPUBufferDescriptor : GPUObjectDescriptorBase {
    required GPUSize64 size;
    required GPUBufferUsageFlags usage;
    boolean mappedAtCreation = false;
};
validating GPUBufferDescriptor(device, descriptor)
  1. If device is lost return false.

  2. If any of the bits of descriptor’s usage aren’t present in this device’s [[allowed buffer usages]] return false.

  3. If both the MAP_READ and MAP_WRITE bits of descriptor’s usage attribute are set, return false.

  4. Return true.

5.2.2. Buffer Usage

typedef [EnforceRange] unsigned long GPUBufferUsageFlags;
[Exposed=(Window, DedicatedWorker)]
namespace GPUBufferUsage {
    const GPUFlagsConstant MAP_READ      = 0x0001;
    const GPUFlagsConstant MAP_WRITE     = 0x0002;
    const GPUFlagsConstant COPY_SRC      = 0x0004;
    const GPUFlagsConstant COPY_DST      = 0x0008;
    const GPUFlagsConstant INDEX         = 0x0010;
    const GPUFlagsConstant VERTEX        = 0x0020;
    const GPUFlagsConstant UNIFORM       = 0x0040;
    const GPUFlagsConstant STORAGE       = 0x0080;
    const GPUFlagsConstant INDIRECT      = 0x0100;
    const GPUFlagsConstant QUERY_RESOLVE = 0x0200;
};
createBuffer(descriptor)

Creates a GPUBuffer.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createBuffer(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUBufferDescriptor Description of the GPUBuffer to create.

Returns: GPUBuffer

  1. If any of the following conditions are unsatisfied, return an error buffer and stop.

    Explain that the resulting error buffer can still be mapped at creation. [Issue #gpuweb/gpuweb#605]

    Explain what are a GPUDevice's [[allowed buffer usages]]. [Issue #gpuweb/gpuweb#605]

  2. Let b be a new GPUBuffer object.

  3. Set b.[[size]] to descriptor.size.

  4. Set b.[[usage]] to descriptor.usage.

  5. If descriptor.mappedAtCreation is true:

    1. Set b.[[mapping]] to a new ArrayBuffer of size b.[[size]].

    2. Set b.[[mapping_range]] to [0, descriptor.size].

    3. Set b.[[mapped_ranges]] to [].

    4. Set b.[[state]] to mapped at creation.

    Else:

    1. Set b.[[mapping]] to null.

    2. Set b.[[mapping_range]] to null.

    3. Set b.[[mapped_ranges]] to null.

    4. Set b.[[state]] to unmapped.

  6. Set each byte of b’s allocation to zero.

  7. Return b.

Note: it is valid to set mappedAtCreation to true without MAP_READ or MAP_WRITE in usage. This can be used to set the buffer’s initial data.

5.3. Buffer Destruction

An application that no longer requires a GPUBuffer can choose to lose access to it before garbage collection by calling destroy().

Note: This allows the user agent to reclaim the GPU memory associated with the GPUBuffer once all previously submitted operations using it are complete.

destroy()

Destroys the GPUBuffer.

Called on: GPUBuffer this.

Returns: undefined

  1. If the this.[[state]] is mapped or mapped at creation:

    1. Run the steps to unmap this.

  2. Set this.[[state]] to destroyed.

Handle error buffers once we have a description of the error monad.

5.4. Buffer Mapping

An application can request to map a GPUBuffer so that they can access its content via ArrayBuffers that represent part of the GPUBuffer's allocations. Mapping a GPUBuffer is requested asynchronously with mapAsync() so that the user agent can ensure the GPU finished using the GPUBuffer before the application can access its content. Once the GPUBuffer is mapped the application can synchronously ask for access to ranges of its content with getMappedRange. A mapped GPUBuffer cannot be used by the GPU and must be unmapped using unmap before work using it can be submitted to the Queue timeline.

Add client-side validation that a mapped buffer can only be unmapped and destroyed on the worker on which it was mapped. Likewise getMappedRange can only be called on that worker. [Issue #gpuweb/gpuweb#605]

typedef [EnforceRange] unsigned long GPUMapModeFlags;
[Exposed=(Window, DedicatedWorker)]
namespace GPUMapMode {
    const GPUFlagsConstant READ  = 0x0001;
    const GPUFlagsConstant WRITE = 0x0002;
};
mapAsync(mode, offset, size)

Maps the given range of the GPUBuffer and resolves the returned Promise when the GPUBuffer's content is ready to be accessed with getMappedRange().

Called on: GPUBuffer this.

Arguments:

Arguments for the GPUBuffer.mapAsync(mode, offset, size) method.
Parameter Type Nullable Optional Description
mode GPUMapModeFlags Whether the buffer should be mapped for reading or writing.
offset GPUSize64 Offset in bytes into the buffer to the start of the range to map.
size GPUSize64 Size in bytes of the range to map.

Returns: Promise<undefined>

Handle error buffers once we have a description of the error monad. [Issue #gpuweb/gpuweb#605]

  1. If size is missing:

    1. Let rangeSize be max(0, this.[[size]] - offset).

    Otherwise, let rangeSize be size.

  2. If any of the following conditions are unsatisfied:

    Do we validate that mode contains only valid flags?

    Then:

    1. Record a validation error on the current scope.

    2. Return a promise rejected with an OperationError on the Device timeline.

  3. Let p be a new Promise.

  4. Set this.[[mapping]] to p.

  5. Set this.[[state]] to mapping pending.

  6. Set this.[[map_mode]] to mode.

  7. Enqueue an operation on the default queue’s Queue timeline that will execute the following:

    1. If this.[[state]] is mapping pending:

      1. Let m be a new ArrayBuffer of size rangeSize.

      2. Set the content of m to the content of this’s allocation starting at offset offset and for rangeSize bytes.

      3. Set this.[[mapping]] to m.

      4. Set this.[[state]] to mapped.

      5. Set this.[[mapping_range]] to [offset, offset + rangeSize].

      6. Set this.[[mapped_ranges]] to [].

    2. Resolve p.

  8. Return p.

getMappedRange(offset, size)

Returns a ArrayBuffer with the contents of the GPUBuffer in the given mapped range.

Called on: GPUBuffer this.

Arguments:

Arguments for the GPUBuffer.getMappedRange(offset, size) method.
Parameter Type Nullable Optional Description
offset GPUSize64 Offset in bytes into the buffer to return buffer contents from.
size GPUSize64 Size in bytes of the ArrayBuffer to return.

Returns: ArrayBuffer

  1. If size is missing:

    1. Let rangeSize be max(0, this.[[size]] - offset).

    Otherwise, let rangeSize be size.

  2. If any of the following conditions are unsatisfied, throw an OperationError and stop.

    Note: It is always valid to get mapped ranges of a GPUBuffer that is mapped at creation, even if it is invalid, because the Content timeline might not know it is invalid.

    Consider aligning mapAsync offset to 8 to match this.

  3. Let m be a new ArrayBuffer of size rangeSize pointing at the content of this.[[mapping]] at offset offset - this.[[mapping_range]][0].

  4. Append m to this.[[mapped_ranges]].

  5. Return m.

unmap()

Unmaps the mapped range of the GPUBuffer and makes it’s contents available for use by the GPU again.

Called on: GPUBuffer this.

Returns: undefined

  1. If any of the following requirements are unmet, generate a validation error and stop.

    Note: It is valid to unmap an invalid GPUBuffer that is mapped at creation because the Content timeline might not know it is an error GPUBuffer.

  2. If this.[[state]] is mapping pending:

    1. Reject [[mapping]] with an AbortError.

    2. Set this.[[mapping]] to null.

  3. If this.[[state]] is mapped or mapped at creation:

    1. If one of the two following conditions holds:

      Then:

      1. Enqueue an operation on the default queue’s Queue timeline that updates the this.[[mapping_range]] of this’s allocation to the content of this.[[mapping]].

    2. Detach each ArrayBuffer in this.[[mapped_ranges]] from its content.

    3. Set this.[[mapping]] to null.

    4. Set this.[[mapping_range]] to null.

    5. Set this.[[mapped_ranges]] to null.

  4. Set this.[[state]] to unmapped.

Note: When a MAP_READ buffer (not currently mapped at creation) is unmapped, any local modifications done by the application to the mapped ranges ArrayBuffer are discarded and will not affect the content of follow-up mappings.

6. Textures and Texture Views

define texture (internal object)

define mipmap level, array layer, aspect, slice (concepts)

6.1. GPUTexture

GPUTextures are created via GPUDevice.createTexture(descriptor) that returns a new texture.

[Exposed=(Window, DedicatedWorker), SecureContext]
interface GPUTexture {
    GPUTextureView createView(optional GPUTextureViewDescriptor descriptor = {});

    undefined destroy();
};
GPUTexture includes GPUObjectBase;

GPUTexture has the following internal slots:

[[descriptor]], of type GPUTextureDescriptor

The GPUTextureDescriptor describing this texture.

All optional fields of GPUTextureDescriptor are defined.

[[destroyed]], of type boolean, initially false

If the texture is destroyed, it can no longer be used in any operation, and its underlying memory can be freed.

compute render extent(baseSize, mipLevel)

Arguments:

Returns: GPUExtent3DDict

  1. Let extent be a new GPUExtent3DDict object.

  2. Set extent.width to max(1, baseSize.widthmipLevel).

  3. Set extent.height to max(1, baseSize.heightmipLevel).

  4. Set extent.depthOrArrayLayers to 1.

  5. Return extent.

share this definition with the part of the specification that describes sampling.

6.1.1. Texture Creation

dictionary GPUTextureDescriptor : GPUObjectDescriptorBase {
    required GPUExtent3D size;
    GPUIntegerCoordinate mipLevelCount = 1;
    GPUSize32 sampleCount = 1;
    GPUTextureDimension dimension = "2d";
    required GPUTextureFormat format;
    required GPUTextureUsageFlags usage;
};
enum GPUTextureDimension {
    "1d",
    "2d",
    "3d",
};
typedef [EnforceRange] unsigned long GPUTextureUsageFlags;
[Exposed=(Window, DedicatedWorker)]
namespace GPUTextureUsage {
    const GPUFlagsConstant COPY_SRC          = 0x01;
    const GPUFlagsConstant COPY_DST          = 0x02;
    const GPUFlagsConstant TEXTURE_BINDING   = 0x04;
    const GPUFlagsConstant STORAGE_BINDING   = 0x08;
    const GPUFlagsConstant RENDER_ATTACHMENT = 0x10;
};
maximum mipLevel count(dimension, size) Arguments:
  1. Calculate the max dimension value m:

  2. Return floor(log2(m)) + 1.

createTexture(descriptor)

Creates a GPUTexture.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createTexture(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUTextureDescriptor Description of the GPUTexture to create.

Returns: GPUTexture

  1. Issue the following steps on the Device timeline of this:

    1. If descriptor.format is a GPUTextureFormat that requires a feature (see § 24.1 Texture Format Capabilities), but this.[[device]].[[features]] does not contain the feature, throw a TypeError.

    2. If any of the following requirements are unmet:

      Then:

      1. Generate a GPUValidationError in the current scope with appropriate error message.

      2. Return a new invalid GPUTexture.

    3. Let t be a new GPUTexture object.

    4. Set t.[[descriptor]] to descriptor.

    5. Return t.

6.1.2. Texture Destruction

An application that no longer requires a GPUTexture can choose to lose access to it before garbage collection by calling destroy().

Note: This allows the user agent to reclaim the GPU memory associated with the GPUTexture once all previously submitted operations using it are complete.

destroy()

Destroys the GPUTexture.

Called on: GPUTexture this.

Returns: undefined

  1. Set this.[[destroyed]] to true.

6.2. GPUTextureView

[Exposed=(Window, DedicatedWorker), SecureContext]
interface GPUTextureView {
};
GPUTextureView includes GPUObjectBase;

GPUTextureView has the following internal slots:

[[texture]]

The GPUTexture into which this is a view.

[[descriptor]]

The GPUTextureViewDescriptor describing this texture view.

All optional fields of GPUTextureViewDescriptor are defined.

[[renderExtent]]

For renderable views, this is the effective GPUExtent3DDict for rendering.

Note: this extent depends on the baseMipLevel.

6.2.1. Texture View Creation

dictionary GPUTextureViewDescriptor : GPUObjectDescriptorBase {
    GPUTextureFormat format;
    GPUTextureViewDimension dimension;
    GPUTextureAspect aspect = "all";
    GPUIntegerCoordinate baseMipLevel = 0;
    GPUIntegerCoordinate mipLevelCount;
    GPUIntegerCoordinate baseArrayLayer = 0;
    GPUIntegerCoordinate arrayLayerCount;
};
enum GPUTextureViewDimension {
    "1d",
    "2d",
    "2d-array",
    "cube",
    "cube-array",
    "3d"
};
enum GPUTextureAspect {
    "all",
    "stencil-only",
    "depth-only"
};
createView(descriptor)

Creates a GPUTextureView.

Called on: GPUTexture this.

Arguments:

Arguments for the GPUTexture.createView(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUTextureViewDescriptor Description of the GPUTextureView to create.

Returns: view, of type GPUTextureView.

  1. Set descriptor to the result of resolving GPUTextureViewDescriptor defaults with descriptor.

  2. Issue the following steps on the Device timeline of this:

    1. If any of the following requirements are unmet:

      Then:

      1. Generate a GPUValidationError in the current scope with appropriate error message.

      2. Return a new invalid GPUTextureView.

    2. Let view be a new GPUTextureView object.

    3. Set view.[[texture]] to this.

    4. Set view.[[descriptor]] to descriptor.

    5. If this.[[descriptor]].usage contains RENDER_ATTACHMENT:

      1. Let renderExtent be compute render extent(this.[[descriptor]].size, descriptor.baseMipLevel).

      2. Set view.[[renderExtent]] to renderExtent.

    6. Return view.

When resolving GPUTextureViewDescriptor defaults for GPUTextureViewDescriptor descriptor run the following steps:
  1. Let resolved be a copy of descriptor.

  2. If resolved.format is undefined, set resolved.format to texture.[[descriptor]].format.

  3. If resolved.mipLevelCount is undefined, set resolved.mipLevelCount to texture.[[descriptor]].mipLevelCountbaseMipLevel.

  4. If resolved.dimension is undefined and texture.[[descriptor]].dimension is:

    "1d"

    Set resolved.dimension to "1d".

    "2d"

    Set resolved.dimension to "2d".

    "3d"

    Set resolved.dimension to "3d".

  5. If resolved.arrayLayerCount is undefined and resolved.dimension is:

    "1d", "2d", or "3d"

    Set resolved.arrayLayerCount to 1.

    "cube"

    Set resolved.arrayLayerCount to 6.

    "2d-array" or "cube-array"

    Set resolved.arrayLayerCount to texture.[[descriptor]].size.depthOrArrayLayersbaseArrayLayer.

  6. Return resolved.

To determine the array layer count of GPUTexture texture, run the following steps:
  1. If texture.[[descriptor]].dimension is:

    "1d" or "3d"

    Return 1.

    "2d"

    Return texture.[[descriptor]].size.depthOrArrayLayers.

6.3. Texture Formats

The name of the format specifies the order of components, bits per component, and data type for the component.

If the format has the -srgb suffix, then sRGB conversions from gamma to linear and vice versa are applied during the reading and writing of color values in the shader. Compressed texture formats are provided by features. Their naming should follow the convention here, with the texture name as a prefix. e.g. etc2-rgba8unorm.

The texel block is a single addressable element of the textures in pixel-based GPUTextureFormats, and a single compressed block of the textures in block-based compressed GPUTextureFormats.

The texel block width and texel block height specifies the dimension of one texel block.

The texel block size of a GPUTextureFormat is the number of bytes to store one texel block. The texel block size of each GPUTextureFormat is constant except for "stencil8", "depth24plus", and "depth24plus-stencil8".

enum GPUTextureFormat {
    // 8-bit formats
    "r8unorm",
    "r8snorm",
    "r8uint",
    "r8sint",

    // 16-bit formats
    "r16uint",
    "r16sint",
    "r16float",
    "rg8unorm",
    "rg8snorm",
    "rg8uint",
    "rg8sint",

    // 32-bit formats
    "r32uint",
    "r32sint",
    "r32float",
    "rg16uint",
    "rg16sint",
    "rg16float",
    "rgba8unorm",
    "rgba8unorm-srgb",
    "rgba8snorm",
    "rgba8uint",
    "rgba8sint",
    "bgra8unorm",
    "bgra8unorm-srgb",
    // Packed 32-bit formats
    "rgb9e5ufloat",
    "rgb10a2unorm",
    "rg11b10ufloat",

    // 64-bit formats
    "rg32uint",
    "rg32sint",
    "rg32float",
    "rgba16uint",
    "rgba16sint",
    "rgba16float",

    // 128-bit formats
    "rgba32uint",
    "rgba32sint",
    "rgba32float",

    // Depth and stencil formats
    "stencil8",
    "depth16unorm",
    "depth24plus",
    "depth24plus-stencil8",
    "depth32float",

    // BC compressed formats usable if "texture-compression-bc" is both
    // supported by the device/user agent and enabled in requestDevice.
    "bc1-rgba-unorm",
    "bc1-rgba-unorm-srgb",
    "bc2-rgba-unorm",
    "bc2-rgba-unorm-srgb",
    "bc3-rgba-unorm",
    "bc3-rgba-unorm-srgb",
    "bc4-r-unorm",
    "bc4-r-snorm",
    "bc5-rg-unorm",
    "bc5-rg-snorm",
    "bc6h-rgb-ufloat",
    "bc6h-rgb-float",
    "bc7-rgba-unorm",
    "bc7-rgba-unorm-srgb",

    // ETC2 compressed formats usable if "texture-compression-etc2" is both
    // supported by the device/user agent and enabled in requestDevice.
    "etc2-rgb8unorm",
    "etc2-rgb8unorm-srgb",
    "etc2-rgb8a1unorm",
    "etc2-rgb8a1unorm-srgb",
    "etc2-rgba8unorm",
    "etc2-rgba8unorm-srgb",
    "eac-r11unorm",
    "eac-r11snorm",
    "eac-rg11unorm",
    "eac-rg11snorm",

    // ASTC compressed formats usable if "texture-compression-astc" is both
    // supported by the device/user agent and enabled in requestDevice.
    "astc-4x4-unorm",
    "astc-4x4-unorm-srgb",
    "astc-5x4-unorm",
    "astc-5x4-unorm-srgb",
    "astc-5x5-unorm",
    "astc-5x5-unorm-srgb",
    "astc-6x5-unorm",
    "astc-6x5-unorm-srgb",
    "astc-6x6-unorm",
    "astc-6x6-unorm-srgb",
    "astc-8x5-unorm",
    "astc-8x5-unorm-srgb",
    "astc-8x6-unorm",
    "astc-8x6-unorm-srgb",
    "astc-8x8-unorm",
    "astc-8x8-unorm-srgb",
    "astc-10x5-unorm",
    "astc-10x5-unorm-srgb",
    "astc-10x6-unorm",
    "astc-10x6-unorm-srgb",
    "astc-10x8-unorm",
    "astc-10x8-unorm-srgb",
    "astc-10x10-unorm",
    "astc-10x10-unorm-srgb",
    "astc-12x10-unorm",
    "astc-12x10-unorm-srgb",
    "astc-12x12-unorm",
    "astc-12x12-unorm-srgb",

    // "depth24unorm-stencil8" feature
    "depth24unorm-stencil8",

    // "depth32float-stencil8" feature
    "depth32float-stencil8",
};

The depth aspect of the "depth24plus") and "depth24plus-stencil8") formats may be implemented as either a 24-bit unsigned normalized value ("depth24unorm") or a 32-bit IEEE 754 floating point value ("depth32float").

add something on GPUAdapter(?) that gives an estimate of the bytes per texel of "stencil8"

The stencil8 format may be implemented as either a real "stencil8", or "depth24stencil8", where the depth aspect is hidden and inaccessible.

Note: While the precision of depth32float is strictly higher than the precision of depth24unorm for all values in the representable range (0.0 to 1.0), note that the set of representable values is not exactly the same: for depth24unorm, 1 ULP has a constant value of 1 / (224 − 1); for depth32float, 1 ULP has a variable value no greater than 1 / (224).

A renderable format is either color renderable format, or depth or stencil renderable format. If a format is listed in § 24.1.1 Plain color formats with RENDER_ATTACHMENT capability, it is a color renderable format. Any other format is not a color renderable format. Any depth/stencil format is a depth or stencil renderable format. Any other format is not a depth or stencil renderable format.

6.4. GPUExternalTexture

A GPUExternalTexture is a sampleable texture wrapping an external video object. The contents of a GPUExternalTexture object may not change, either from inside WebGPU (it is only sampleable) or from outside WebGPU (e.g. due to video frame advancement).

Update this description with canvas.

They are bound into bind group layouts using the externalTexture bind group layout entry member. External textures use several binding slots: see Exceeds the binding slot limits.

External textures can be implemented without creating a copy of the imported source, but this depends implementation-defined factors. Ownership of the underlying representation may either be exclusive or shared with other owners (such as a video decoder), but this is not visible to the application.

The underlying representation of an external texture is unobservable (except for sampling behavior) but typically may include

The configuration used may not be stable across time, systems, user agents, media sources, or frames within a single video source. In order to account for many possible representations, the binding conservatively uses the following, for each external texture:

[Exposed=(Window, DedicatedWorker), SecureContext]
interface GPUExternalTexture {
};
GPUExternalTexture includes GPUObjectBase;

GPUExternalTexture has the following internal slots:

[[destroyed]], of type boolean

Indicates whether the object has been destroyed (can no longer be used). Initially set to false.

6.4.1. Importing External Textures

An external texture is created from an external video object using importExternalTexture().

Update this description with canvas.

External textures are destroyed automatically, as a microtask, instead of manually or upon garbage collection like other resources.

dictionary GPUExternalTextureDescriptor : GPUObjectDescriptorBase {
    required HTMLVideoElement source;
    GPUPredefinedColorSpace colorSpace = "srgb";
};
importExternalTexture(descriptor)

Creates a GPUExternalTexture wrapping the provided image source.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.importExternalTexture(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUExternalTextureDescriptor Provides the external image source object (and any creation options).

Returns: GPUExternalTexture

  1. Let source be descriptor.source.

  2. Let usability be the result of checking the usability of source (which may throw an exception).

  3. If usability is bad, throw an InvalidStateError and stop.

  4. If source is not origin-clean, throw a SecurityError and stop.

  5. Let data be the result of converting the current image contents of source into the color space descriptor.colorSpace with unpremultiplied alpha.

    Note: This is described like a copy, but may be implemented as a reference to read-only underlying data plus appropriate metadata to perform conversion later.

    It is currently undetermined whether the default colorSpace, "srgb", is extended-srgb or clamped-srgb. This will be determined upstream as the semantics around super-srgb image sources get defined. Unfortunately we can’t sidestep it for now because video sources can go already go outside the srgb range. The upstream determination will change whether using the default colorSpace option can result in sampling values greater than 1.0 or not. If upstream decides to make "srgb" mean clamped-srgb, we also have the option of changing our default to "extended-srgb".

  6. Let result be a new GPUExternalTexture object wrapping data.

  7. Queue a microtask to set result.[[destroyed]] to true, releasing the underlying resource.

    Is this too restrictive?

  8. Return result.

6.4.2. Sampling External Textures

External textures are represented in WGSL with texture_external and may be read using textureLoad and textureSampleLevel.

The sampler provided to textureSampleLevel is used to sample the underlying textures. The result is in the color space set by colorSpace. It is implementation-dependent whether, for any given external texture, the sampler (and filtering) is applied before or after conversion from underlying values into the specified color space.

Note: If the internal representation is an RGBA plane, sampling behaves as on a regular 2D texture. If there are several underlying planes (e.g. Y+UV), the sampler is used to sample each underlying texture separately, prior to conversion from YUV to the specified color space.

7. Samplers

7.1. GPUSampler

A GPUSampler encodes transformations and filtering information that can be used in a shader to interpret texture resource data.

GPUSamplers are created via GPUDevice.createSampler(optional descriptor) that returns a new sampler object.

[Exposed=(Window, DedicatedWorker), SecureContext]
interface GPUSampler {
};
GPUSampler includes GPUObjectBase;

GPUSampler has the following internal slots:

[[descriptor]], of type GPUSamplerDescriptor, readonly

The GPUSamplerDescriptor with which the GPUSampler was created.

[[isComparison]] of type boolean.

Whether the GPUSampler is used as a comparison sampler.

[[isFiltering]] of type boolean.

Whether the GPUSampler weights multiple samples of a texture.

7.2. Sampler Creation

7.2.1. GPUSamplerDescriptor

A GPUSamplerDescriptor specifies the options to use to create a GPUSampler.

dictionary GPUSamplerDescriptor : GPUObjectDescriptorBase {
    GPUAddressMode addressModeU = "clamp-to-edge";
    GPUAddressMode addressModeV = "clamp-to-edge";
    GPUAddressMode addressModeW = "clamp-to-edge";
    GPUFilterMode magFilter = "nearest";
    GPUFilterMode minFilter = "nearest";
    GPUFilterMode mipmapFilter = "nearest";
    float lodMinClamp = 0;
    float lodMaxClamp = 32;
    GPUCompareFunction compare;
    [Clamp] unsigned short maxAnisotropy = 1;
};

explain how LOD is calculated and if there are differences here between platforms.

explain what anisotropic sampling is

GPUAddressMode describes the behavior of the sampler if the sample footprint extends beyond the bounds of the sampled texture.

Describe a "sample footprint" in greater detail.

enum GPUAddressMode {
    "clamp-to-edge",
    "repeat",
    "mirror-repeat"
};
"clamp-to-edge"

Texture coordinates are clamped between 0.0 and 1.0, inclusive.

"repeat"

Texture coordinates wrap to the other side of the texture.

"mirror-repeat"

Texture coordinates wrap to the other side of the texture, but the texture is flipped when the integer part of the coordinate is odd.

GPUFilterMode describes the behavior of the sampler if the sample footprint does not exactly match one texel.

enum GPUFilterMode {
    "nearest",
    "linear"
};
"nearest"

Return the value of the texel nearest to the texture coordinates.

"linear"

Select two texels in each dimension and return a linear interpolation between their values.

GPUCompareFunction specifies the behavior of a comparison sampler. If a comparison sampler is used in a shader, an input value is compared to the sampled texture value, and the result of this comparison test (0.0f for pass, or 1.0f for fail) is used in the filtering operation.

describe how filtering interacts with comparison sampling.

enum GPUCompareFunction {
    "never",
    "less",
    "equal",
    "less-equal",
    "greater",
    "not-equal",
    "greater-equal",
    "always"
};
"never"

Comparison tests never pass.

"less"

A provided value passes the comparison test if it is less than the sampled value.

"equal"

A provided value passes the comparison test if it is equal to the sampled value.

"less-equal"

A provided value passes the comparison test if it is less than or equal to the sampled value.

"greater"

A provided value passes the comparison test if it is greater than the sampled value.

"not-equal"

A provided value passes the comparison test if it is not equal to the sampled value.

"greater-equal"

A provided value passes the comparison test if it is greater than or equal to the sampled value.

"always"

Comparison tests always pass.

validating GPUSamplerDescriptor(device, descriptor) Arguments:

Returns: boolean

Return true if and only if all of the following conditions are satisfied:

createSampler(descriptor)

Creates a GPUBindGroupLayout.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createSampler(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUSamplerDescriptor Description of the GPUSampler to create.

Returns: GPUSampler

  1. Let s be a new GPUSampler object.

  2. Set s.[[descriptor]] to descriptor.

  3. Set s.[[isComparison]] to false if the compare attribute of s.[[descriptor]] is null or undefined. Otherwise, set it to true.

  4. Set s.[[isFiltering]] to false if none of minFilter, magFilter, or mipmapFilter has the value of "linear". Otherwise, set it to true.

  5. Return s.

Valid Usage

8. Resource Binding

8.1. GPUBindGroupLayout

A GPUBindGroupLayout defines the interface between a set of resources bound in a GPUBindGroup and their accessibility in shader stages.

[Exposed=(Window, DedicatedWorker), SecureContext]
interface GPUBindGroupLayout {
};
GPUBindGroupLayout includes GPUObjectBase;

GPUBindGroupLayout has the following internal slots:

[[descriptor]]

8.1.1. Creation

A GPUBindGroupLayout is created via GPUDevice.createBindGroupLayout().

dictionary GPUBindGroupLayoutDescriptor : GPUObjectDescriptorBase {
    required sequence<GPUBindGroupLayoutEntry> entries;
};

A GPUBindGroupLayoutEntry describes a single shader resource binding to be included in a GPUBindGroupLayout.

typedef [EnforceRange] unsigned long GPUShaderStageFlags;
[Exposed=(Window, DedicatedWorker)]
namespace GPUShaderStage {
    const GPUFlagsConstant VERTEX   = 0x1;
    const GPUFlagsConstant FRAGMENT = 0x2;
    const GPUFlagsConstant COMPUTE  = 0x4;
};

dictionary GPUBindGroupLayoutEntry {
    required GPUIndex32 binding;
    required GPUShaderStageFlags visibility;

    GPUBufferBindingLayout buffer;
    GPUSamplerBindingLayout sampler;
    GPUTextureBindingLayout texture;
    GPUStorageTextureBindingLayout storageTexture;
    GPUExternalTextureBindingLayout externalTexture;
};

GPUBindGroupLayoutEntry dictionaries have the following members:

binding, of type GPUIndex32

A unique identifier for a resource binding within a GPUBindGroupLayoutEntry, a corresponding GPUBindGroupEntry, and the GPUShaderModules.

visibility, of type GPUShaderStageFlags

A bitset of the members of GPUShaderStage. Each set bit indicates that a GPUBindGroupLayoutEntry's resource will be accessible from the associated shader stage.

buffer, of type GPUBufferBindingLayout

When not undefined, indicates the binding resource type for this GPUBindGroupLayoutEntry is GPUBufferBinding.

sampler, of type GPUSamplerBindingLayout

When not undefined, indicates the binding resource type for this GPUBindGroupLayoutEntry is GPUSampler.

texture, of type GPUTextureBindingLayout

When not undefined, indicates the binding resource type for this GPUBindGroupLayoutEntry is GPUTextureView.

storageTexture, of type GPUStorageTextureBindingLayout

When not undefined, indicates the binding resource type for this GPUBindGroupLayoutEntry is GPUTextureView.

externalTexture, of type GPUExternalTextureBindingLayout

When not undefined, indicates the binding resource type for this GPUBindGroupLayoutEntry is GPUExternalTexture.

The binding member of a GPUBindGroupLayoutEntry is determined by which member of the GPUBindGroupLayoutEntry is defined: buffer, sampler, texture, storageTexture, or externalTexture. Only one may be defined for any given GPUBindGroupLayoutEntry. Each member has an associated GPUBindingResource type and each binding type has an associated internal usage, given by this table:

Binding member Resource type Binding type
Binding usage
buffer GPUBufferBinding "uniform" constant
"storage" storage
"read-only-storage" storage-read
sampler GPUSampler "filtering" constant
"non-filtering"
"comparison"
texture GPUTextureView "float" constant
"unfilterable-float"
"depth"
"sint"
"uint"
storageTexture GPUTextureView "write-only" storage
externalTexture GPUExternalTexture constant
The list of GPUBindGroupLayoutEntry values entries exceeds the binding slot limits of supported limits limits if the number of slots used toward a limit exceeds the supported value in limits. Each entry may use multiple slots toward multiple limits.
  1. For each entry in entries, if:

    entry.buffer?.type is "uniform" and entry.buffer?.hasDynamicOffset is true

    Consider 1 maxDynamicUniformBuffersPerPipelineLayout slot to be used.

    entry.buffer?.type is "storage" and entry.buffer?.hasDynamicOffset is true

    Consider 1 maxDynamicStorageBuffersPerPipelineLayout slot to be used.

  2. For each shader stage stage in « VERTEX, FRAGMENT, COMPUTE »:

    1. For each entry in entries for which entry.visibility contains stage, if:

      entry.buffer?.type is "uniform"

      Consider 1 maxUniformBuffersPerShaderStage slot to be used.

      entry.buffer?.type is "storage" or "read-only-storage"

      Consider 1 maxStorageBuffersPerShaderStage slot to be used.

      entry.sampler is not undefined

      Consider 1 maxSamplersPerShaderStage slot to be used.

      entry.texture is not undefined

      Consider 1 maxSampledTexturesPerShaderStage slot to be used.

      entry.storageTexture is not undefined

      Consider 1 maxStorageTexturesPerShaderStage slot to be used.

      entry.externalTexture is not undefined

      Consider 4 maxSampledTexturesPerShaderStage slot, 1 maxSamplersPerShaderStage slot, and 1 maxUniformBuffersPerShaderStage slot to be used.

enum GPUBufferBindingType {
    "uniform",
    "storage",
    "read-only-storage",
};

dictionary GPUBufferBindingLayout {
    GPUBufferBindingType type = "uniform";
    boolean hasDynamicOffset = false;
    GPUSize64 minBindingSize = 0;
};

GPUBufferBindingLayout dictionaries have the following members:

type, of type GPUBufferBindingType, defaulting to "uniform"

Indicates the type required for buffers bound to this bindings.

hasDynamicOffset, of type boolean, defaulting to false

Indicates whether this binding requires a dynamic offset.

minBindingSize, of type GPUSize64, defaulting to 0

May be used to indicate the minimum buffer binding size.

enum GPUSamplerBindingType {
    "filtering",
    "non-filtering",
    "comparison",
};

dictionary GPUSamplerBindingLayout {
    GPUSamplerBindingType type = "filtering";
};

GPUSamplerBindingLayout dictionaries have the following members:

type, of type GPUSamplerBindingType, defaulting to "filtering"

Indicates the required type of a sampler bound to this bindings.

enum GPUTextureSampleType {
  "float",
  "unfilterable-float",
  "depth",
  "sint",
  "uint",
};

dictionary GPUTextureBindingLayout {
    GPUTextureSampleType sampleType = "float";
    GPUTextureViewDimension viewDimension = "2d";
    boolean multisampled = false;
};

consider making sampleType truly optional.

GPUTextureBindingLayout dictionaries have the following members:

sampleType, of type GPUTextureSampleType, defaulting to "float"

Indicates the type required for texture views bound to this binding.

viewDimension, of type GPUTextureViewDimension, defaulting to "2d"

Indicates the required dimension for texture views bound to this binding.

multisampled, of type boolean, defaulting to false

Inicates whether or not texture views bound to this binding must be multisampled.

enum GPUStorageTextureAccess {
    "write-only",
};

dictionary GPUStorageTextureBindingLayout {
    GPUStorageTextureAccess access = "write-only";
    required GPUTextureFormat format;
    GPUTextureViewDimension viewDimension = "2d";
};

consider making format truly optional.

GPUStorageTextureBindingLayout dictionaries have the following members:

access, of type GPUStorageTextureAccess, defaulting to "write-only"

Indicates whether texture views bound to this binding will be bound for read-only or write-only access.

format, of type GPUTextureFormat

The required format of texture views bound to this binding.

viewDimension, of type GPUTextureViewDimension, defaulting to "2d"

Indicates the required dimension for texture views bound to this binding.

dictionary GPUExternalTextureBindingLayout {
};

A GPUBindGroupLayout object has the following internal slots:

[[entryMap]] of type ordered map<GPUSize32, GPUBindGroupLayoutEntry>.

The map of binding indices pointing to the GPUBindGroupLayoutEntrys, which this GPUBindGroupLayout describes.

[[dynamicOffsetCount]] of type GPUSize32.

The number of buffer bindings with dynamic offsets in this GPUBindGroupLayout.

[[exclusivePipeline]] of type GPUPipelineBase?, initially null.

The pipeline that created this GPUBindGroupLayout, if it was created as part of a default pipeline layout. If not null, GPUBindGroups created with this GPUBindGroupLayout can only be used with the specified GPUPipelineBase.

createBindGroupLayout(descriptor)

Creates a GPUBindGroupLayout.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createBindGroupLayout(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUBindGroupLayoutDescriptor Description of the GPUBindGroupLayout to create.

Returns: GPUBindGroupLayout

  1. Let layout be a new valid GPUBindGroupLayout object.

  2. Set layout.[[descriptor]] to descriptor.

  3. Issue the following steps on the Device timeline of this:

    1. If any of the following conditions are unsatisfied:

      Then:

      1. Generate a GPUValidationError in the current scope with appropriate error message.

      2. Make layout invalid and return layout.

    2. Set layout.[[dynamicOffsetCount]] to the number of entries in descriptor where buffer is not undefined and buffer.hasDynamicOffset is true.

    3. For each GPUBindGroupLayoutEntry entry in descriptor.entries:

      1. Insert entry into layout.[[entryMap]] with the key of entry.binding.

  4. Return layout.

8.1.2. Compatibility

Two GPUBindGroupLayout objects a and b are considered group-equivalent if and only if all of the following conditions are satisfied:

If bind groups layouts are group-equivalent they can be interchangeably used in all contents.

8.2. GPUBindGroup

A GPUBindGroup defines a set of resources to be bound together in a group and how the resources are used in shader stages.

[Exposed=(Window, DedicatedWorker), SecureContext]
interface GPUBindGroup {
};
GPUBindGroup includes GPUObjectBase;

8.2.1. Bind Group Creation

A GPUBindGroup is created via GPUDevice.createBindGroup().

dictionary GPUBindGroupDescriptor : GPUObjectDescriptorBase {
    required GPUBindGroupLayout layout;
    required sequence<GPUBindGroupEntry> entries;
};

A GPUBindGroupEntry describes a single resource to be bound in a GPUBindGroup.

typedef (GPUSampler or GPUTextureView or GPUBufferBinding or GPUExternalTexture) GPUBindingResource;

dictionary GPUBindGroupEntry {
    required GPUIndex32 binding;
    required GPUBindingResource resource;
};
dictionary GPUBufferBinding {
    required GPUBuffer buffer;
    GPUSize64 offset = 0;
    GPUSize64 size;
};

A GPUBindGroup object has the following internal slots:

[[layout]] of type GPUBindGroupLayout.

The GPUBindGroupLayout associated with this GPUBindGroup.

[[entries]] of type sequence<GPUBindGroupEntry>.

The set of GPUBindGroupEntrys this GPUBindGroup describes.

[[usedResources]] of type ordered map<subresource, list<internal usage>>.

The set of buffer and texture subresources used by this bind group, associated with lists of the internal usage flags.

createBindGroup(descriptor)

Creates a GPUBindGroup.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createBindGroup(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUBindGroupDescriptor Description of the GPUBindGroup to create.

Returns: GPUBindGroup

  1. Let bindGroup be a new valid GPUBindGroup object.

  2. Let limits be this.[[device]].[[limits]].

  3. Issue the following steps on the Device timeline of this:

    1. If any of the following conditions are unsatisfied:

      For each GPUBindGroupEntry bindingDescriptor in descriptor.entries:

      Then:

      1. Generate a GPUValidationError in the current scope with appropriate error message.

      2. Make bindGroup invalid and return bindGroup.

    2. Let bindGroup.[[layout]] = descriptor.layout.

    3. Let bindGroup.[[entries]] = descriptor.entries.

    4. Let bindGroup.[[usedResources]] = {}.

    5. For each GPUBindGroupEntry bindingDescriptor in descriptor.entries:

      1. Let internalUsage be the binding usage for layoutBinding.

      2. Each subresource seen by resource is added to [[usedResources]] as internalUsage.

  4. Return bindGroup.

define the "effective buffer binding size" separately.

8.3. GPUPipelineLayout

A GPUPipelineLayout defines the mapping between resources of all GPUBindGroup objects set up during command encoding in setBindGroup, and the shaders of the pipeline set by GPURenderEncoderBase.setPipeline or GPUComputePassEncoder.setPipeline.

The full binding address of a resource can be defined as a trio of:

  1. shader stage mask, to which the resource is visible

  2. bind group index

  3. binding number

The components of this address can also be seen as the binding space of a pipeline. A GPUBindGroup (with the corresponding GPUBindGroupLayout) covers that space for a fixed bind group index. The contained bindings need to be a superset of the resources used by the shader at this bind group index.

[Exposed=(Window, DedicatedWorker), SecureContext]
interface GPUPipelineLayout {
};
GPUPipelineLayout includes GPUObjectBase;

GPUPipelineLayout has the following internal slots:

[[bindGroupLayouts]] of type list<GPUBindGroupLayout>.

The GPUBindGroupLayout objects provided at creation in GPUPipelineLayoutDescriptor.bindGroupLayouts.

Note: using the same GPUPipelineLayout for many GPURenderPipeline or GPUComputePipeline pipelines guarantees that the user agent doesn’t need to rebind any resources internally when there is a switch between these pipelines.

GPUComputePipeline object X was created with GPUPipelineLayout.bindGroupLayouts A, B, C. GPUComputePipeline object Y was created with GPUPipelineLayout.bindGroupLayouts A, D, C. Supposing the command encoding sequence has two dispatches:
  1. setBindGroup(0, ...)

  2. setBindGroup(1, ...)

  3. setBindGroup(2, ...)

  4. setPipeline(X)

  5. dispatch()

  6. setBindGroup(1, ...)

  7. setPipeline(Y)

  8. dispatch()

In this scenario, the user agent would have to re-bind the group slot 2 for the second dispatch, even though neither the GPUBindGroupLayout at index 2 of GPUPipelineLayout.bindGrouplayouts, or the GPUBindGroup at slot 2, change.

should this example and the note be moved to some "best practices" document?

Note: the expected usage of the GPUPipelineLayout is placing the most common and the least frequently changing bind groups at the "bottom" of the layout, meaning lower bind group slot numbers, like 0 or 1. The more frequently a bind group needs to change between draw calls, the higher its index should be. This general guideline allows the user agent to minimize state changes between draw calls, and consequently lower the CPU overhead.

8.3.1. Creation

A GPUPipelineLayout is created via GPUDevice.createPipelineLayout().

dictionary GPUPipelineLayoutDescriptor : GPUObjectDescriptorBase {
    required sequence<GPUBindGroupLayout> bindGroupLayouts;
};
createPipelineLayout(descriptor)

Creates a GPUPipelineLayout.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createPipelineLayout(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUPipelineLayoutDescriptor Description of the GPUPipelineLayout to create.

Returns: GPUPipelineLayout

  1. If any of the following requirements are unmet:

    Let limits be this.[[device]].[[limits]].

    Let allEntries be the result of concatenating bgl.[[descriptor]].entries for all bgl in descriptor.bindGroupLayouts.

    Then:

    1. Generate a GPUValidationError in the current scope with appropriate error message.

    2. Create a new invalid GPUPipelineLayout and return the result.

  2. Let pl be a new GPUPipelineLayout object.

  3. Set the pl.[[bindGroupLayouts]] to descriptor.bindGroupLayouts.

  4. Return pl.

Note: two GPUPipelineLayout objects are considered equivalent for any usage if their internal [[bindGroupLayouts]] sequences contain GPUBindGroupLayout objects that are group-equivalent.

9. Shader Modules

9.1. GPUShaderModule

[Exposed=(Window, DedicatedWorker), SecureContext]
interface GPUShaderModule {
    Promise<GPUCompilationInfo> compilationInfo();
};
GPUShaderModule includes GPUObjectBase;

GPUShaderModule is Serializable. It is a reference to an internal shader module object, and Serializable means that the reference can be copied between realms (threads/workers), allowing multiple realms to access it concurrently. Since GPUShaderModule is immutable, there are no race conditions.

Finish defining multithreading API and add [Serializable] back to the interface. [Issue #gpuweb/gpuweb#354]

9.1.1. Shader Module Creation

dictionary GPUShaderModuleDescriptor : GPUObjectDescriptorBase {
    required USVString code;
    object sourceMap;
};

sourceMap, if defined, MAY be interpreted as a source-map-v3 format. Source maps are optional, but serve as a standardized way to support dev-tool integration such as source-language debugging. [SourceMap]

createShaderModule(descriptor)

Creates a GPUShaderModule.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createShaderModule(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUShaderModuleDescriptor Description of the GPUShaderModule to create.

Returns: GPUShaderModule

Describe createShaderModule() algorithm steps.

9.1.2. Shader Module Compilation Information

enum GPUCompilationMessageType {
    "error",
    "warning",
    "info"
};

[Exposed=(Window, DedicatedWorker), Serializable, SecureContext]
interface GPUCompilationMessage {
    readonly attribute DOMString message;
    readonly attribute GPUCompilationMessageType type;
    readonly attribute unsigned long long lineNum;
    readonly attribute unsigned long long linePos;
    readonly attribute unsigned long long offset;
    readonly attribute unsigned long long length;
};

[Exposed=(Window, DedicatedWorker), Serializable, SecureContext]
interface GPUCompilationInfo {
    readonly attribute FrozenArray<GPUCompilationMessage> messages;
};

A GPUCompilationMessage is an informational, warning, or error message generated by the GPUShaderModule compiler. The messages are intended to be human readable to help developers diagnose issues with their shader code. Each message may correspond to either a single point in the shader code, a substring of the shader code, or may not correspond to any specific point in the code at all.

GPUCompilationMessage has the following attributes:

message, of type DOMString, readonly

A human-readable string containing the message generated during the shader compilation.

type, of type GPUCompilationMessageType, readonly

The severity level of the message.

lineNum, of type unsigned long long, readonly

The line number in the shader code the message corresponds to. Value is one-based, such that a lineNum of 1 indicates the first line of the shader code.

If the message corresponds to a substring this points to the line on which the substring begins. Must be 0 if the message does not correspond to any specific point in the shader code.

Reference WGSL spec when it defines what a line is.

linePos, of type unsigned long long, readonly

The offset, in UTF-16 code units, from the beginning of line lineNum of the shader code to the point or beginning of the substring that the message corresponds to. Value is one-based, such that a linePos of 1 indicates the first character of the line.

If message corresponds to a substring this points to the first UTF-16 code unit of the substring. Must be 0 if the message does not correspond to any specific point in the shader code.

offset, of type unsigned long long, readonly

The offset from the beginning of the shader code in UTF-16 code units to the point or beginning of the substring that message corresponds to. Must reference the same position as lineNum and linePos. Must be 0 if the message does not correspond to any specific point in the shader code.

length, of type unsigned long long, readonly

The number of UTF-16 code units in the substring that message corresponds to. If the message does not correspond with a substring then length must be 0.

Note: GPUCompilationMessage.lineNum and GPUCompilationMessage.linePos are one-based since the most common use for them is expected to be printing human readable messages that can be correlated with the line and column numbers shown in many text editors.

Note: GPUCompilationMessage.offset and GPUCompilationMessage.length are appropriate to pass to substr() in order to retrieve the substring of the shader code the message corresponds to.

compilationInfo()

Returns any messages generated during the GPUShaderModule's compilation.

Called on: GPUShaderModule this.

Returns: Promise<GPUCompilationInfo>

Describe compilationInfo() algorithm steps.

10. Pipelines

A pipeline, be it GPUComputePipeline or GPURenderPipeline, represents the complete function done by a combination of the GPU hardware, the driver, and the user agent, that process the input data in the shape of bindings and vertex buffers, and produces some output, like the colors in the output render targets.

Structurally, the pipeline consists of a sequence of programmable stages (shaders) and fixed-function states, such as the blending modes.

Note: Internally, depending on the target platform, the driver may convert some of the fixed-function states into shader code, and link it together with the shaders provided by the user. This linking is one of the reason the object is created as a whole.

This combination state is created as a single object (by GPUDevice.createComputePipeline() or GPUDevice.createRenderPipeline()), and switched as one (by GPUComputePassEncoder.setPipeline or GPURenderEncoderBase.setPipeline correspondingly).

10.1. Base pipelines

dictionary GPUPipelineDescriptorBase : GPUObjectDescriptorBase {
    GPUPipelineLayout layout;
};

interface mixin GPUPipelineBase {
    GPUBindGroupLayout getBindGroupLayout(unsigned long index);
};

GPUPipelineBase has the following internal slots:

[[layout]] of type GPUPipelineLayout.

The definition of the layout of resources which can be used with this.

GPUPipelineBase has the following methods:

getBindGroupLayout(index)

Gets a GPUBindGroupLayout that is compatible with the GPUPipelineBase's GPUBindGroupLayout at index.

Called on: GPUPipelineBase this.

Arguments:

Arguments for the GPUPipelineBase.getBindGroupLayout(index) method.
Parameter Type Nullable Optional Description
index unsigned long Index into the pipeline layout’s [[bindGroupLayouts]] sequence.

Returns: GPUBindGroupLayout

  1. If indexthis.[[device]].[[limits]].maxBindGroups:

    1. Throw a RangeError.

  2. If this is not valid:

    1. Return a new error GPUBindGroupLayout.

  3. Return a new GPUBindGroupLayout object that references the same internal object as this.[[layout]].[[bindGroupLayouts]][index].

Specify this more properly once we have internal objects for GPUBindGroupLayout. Alternatively only spec is as a new internal objects that’s group-equivalent

Note: Only returning new GPUBindGroupLayout objects ensures no synchronization is necessary between the Content timeline and the Device timeline.

10.1.1. Default pipeline layout

A GPUPipelineBase object that was created without a layout has a default layout created and used instead.

To create a default pipeline layout for GPUPipelineBase pipeline, run the following steps:

  1. Let groupDescs be a sequence of device.[[limits]].maxBindGroups new GPUBindGroupLayoutDescriptor objects.

  2. For each groupDesc in groupDescs:

    1. Set groupDesc.entries to an empty sequence.

  3. For each GPUProgrammableStage stageDesc in the descriptor used to create pipeline:

    1. Let stageInfo be the "reflection information" for stageDesc.

      Define the reflection information concept so that this spec can interface with the WGSL spec and get information what the interface is for a GPUShaderModule for a specific entrypoint.

    2. Let shaderStage be the GPUShaderStageFlags for stageDesc.entryPoint in stageDesc.module.

    3. For each resource resource in stageInfo’s resource interface:

      1. Let group be resource’s "group" decoration.

      2. Let binding be resource’s "binding" decoration.

      3. Let entry be a new GPUBindGroupLayoutEntry.

      4. Set entry.binding to binding.

      5. Set entry.visibility to shaderStage.

      6. If resource is for a sampler binding:

        1. Let samplerLayout be a new GPUSamplerBindingLayout.

        2. Set entry.sampler to samplerLayout.

      7. If resource is for a comparison sampler binding:

        1. Let samplerLayout be a new GPUSamplerBindingLayout.

        2. Set samplerLayout.type to "comparison".

        3. Set entry.sampler to samplerLayout.

      8. If resource is for a buffer binding:

        1. Let bufferLayout be a new GPUBufferBindingLayout.

        2. Set bufferLayout.minBindingSize to resource’s minimum buffer binding size.

          link to a definition for "minimum buffer binding size" in the "reflection information".

        3. If resource is for a read-only storage buffer:

          1. Set bufferLayout.type to "read-only-storage".

        4. If resource is for a storage buffer:

          1. Set bufferLayout.type to "storage".

        5. Set entry.buffer to bufferLayout.

      9. If resource is for a sampled texture binding:

        1. Let textureLayout be a new GPUTextureBindingLayout.

        2. If resource is a depth texture binding:

          Else if the sampled type of resource is:

        3. Set textureLayout.viewDimension to resource’s dimension.

        4. If resource is for a multisampled texture:

          1. Set textureLayout.multisampled to true.

        5. Set entry.texture to textureLayout.

      10. If resource is for a storage texture binding:

        1. Let storageTextureLayout be a new GPUStorageTextureBindingLayout.

        2. Set storageTextureLayout.format to resource’s format.

        3. Set storageTextureLayout.viewDimension to resource’s dimension.

        4. If resource is for a write-only storage texture:

          1. Set storageTextureLayout.access to "write-only".

        5. Set entry.storageTexture to storageTextureLayout.

      11. If groupDescs[group] has an entry previousEntry with binding equal to binding:

        1. If entry has different visibility than previousEntry:

          1. Add the bits set in entry.visibility into previousEntry.visibility

        2. If resource is for a buffer binding and entry has greater buffer.minBindingSize than previousEntry:

          1. Set previousEntry.buffer.minBindingSize to entry.buffer.minBindingSize.

        3. If resource is a sampled texture binding and entry has different texture.sampleType than previousEntry and both entry and previousEntry have texture.sampleType of either "float" or "unfilterable-float":

          1. Set previousEntry.texture.sampleType to "float".

        4. If any other property is unequal between entry and previousEntry:

          1. Return null (which will cause the creation of the pipeline to fail).

      12. Else

        1. Append entry to groupDescs[group].

  4. Let groupLayouts be a new sequence.

  5. For each groupDesc in groupDescs:

    1. Let bindGroupLayout be the result of calling device.createBindGroupLayout()(groupDesc).

    2. Set bindGroupLayout.[[exclusivePipeline]] to pipeline.

    3. Append bindGroupLayout to groupLayouts.

  6. Let desc be a new GPUPipelineLayoutDescriptor.

  7. Set desc.bindGroupLayouts to groupLayouts.

  8. Return device.createPipelineLayout()(desc).

This fills the pipeline layout with empty bindgroups. Revisit once the behavior of empty bindgroups is specified.

10.1.2. GPUProgrammableStage

A GPUProgrammableStage describes the entry point in the user-provided GPUShaderModule that controls one of the programmable stages of a pipeline.

dictionary GPUProgrammableStage {
    required GPUShaderModule module;
    required USVString entryPoint;
    record<USVString, GPUPipelineConstantValue> constants;
};

typedef double GPUPipelineConstantValue; // May represent WGSL’s bool, f32, i32, u32.
constants, of type record<USVString, GPUPipelineConstantValue>

Specifies the values of pipeline-overridable constants in the shader module module.

Each such pipeline-overridable constant is uniquely identified by a single pipeline-overridable constant identifier string (representing the numeric ID of the constant, if one is specified, and otherwise the constant’s identifier name).

The key of each key-value pair must equal the identifier string of one such constant. When the pipeline is executed, that constant will have the specified value.

Values are specified as GPUPipelineConstantValue, which is a double which is converted to the WGSL data type of the corresponding pipeline-overridable constant (bool, i32, u32, or f32) via an IDL value (boolean, long, unsigned long, or float).

Pipeline-overridable constants defined in WGSL:
[[override(0)]]    let has_point_light: bool = true; // Algorithmic control.
[[override(1200)]] let specular_param: f32 = 2.3;    // Numeric control.
[[override(1300)]] let gain: f32;                    // Must be overridden.
[[override]]       let width: f32 = 0.0;             // Specifed at the API level
                                                     //   using the name "width".
[[override]]       let depth: f32;                   // Specifed at the API level
                                                     //   using the name "depth".
                                                     //   Must be overridden.

Corresponding JavaScript code, providing only the overrides which are required (have no defaults):

{
    // ...
    constants: {
        1300: 2.0,  // "gain"
        depth: -1,  // "depth"
    }
}

Corresponding JavaScript code, overriding all constants:

{
    // ...
    constants: {
        0: false,   // "has_point_light"
        1200: 3.0,  // "specular_param"
        1300: 2.0,  // "gain"
        width: 20,  // "width"
        depth: -1,  // "depth"
    }
}
validating GPUProgrammableStage(stage, descriptor, layout)

Arguments:

Return true if all of the following conditions are met:

validating shader binding(binding, layout)

Arguments:

Let bindGroup be the bind group index, and bindIndex be the binding index, of the shader binding declaration variable.

Return true if all of the following conditions are satisfied:

A resource binding is considered to be statically used by a shader entry point if and only if it’s reachable by the control flow graph of the shader module, starting at the entry point.

10.2. GPUComputePipeline

A GPUComputePipeline is a kind of pipeline that controls the compute shader stage, and can be used in GPUComputePassEncoder.

Compute inputs and outputs are all contained in the bindings, according to the given GPUPipelineLayout. The outputs correspond to buffer bindings with a type of "storage" and storageTexture bindings with a type of "write-only".

Stages of a compute pipeline:

  1. Compute shader

[Exposed=(Window, DedicatedWorker), SecureContext]
interface GPUComputePipeline {
};
GPUComputePipeline includes GPUObjectBase;
GPUComputePipeline includes GPUPipelineBase;

10.2.1. Creation

dictionary GPUComputePipelineDescriptor : GPUPipelineDescriptorBase {
    required GPUProgrammableStage compute;
};
createComputePipeline(descriptor)

Creates a GPUComputePipeline.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createComputePipeline(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUComputePipelineDescriptor Description of the GPUComputePipeline to create.

Returns: GPUComputePipeline

  1. Let pipeline be a new valid GPUComputePipeline object.

  2. Issue the following steps on the Device timeline of this:

    1. If any of the following conditions are unsatisfied:

      Then:

      1. Generate a GPUValidationError in the current scope with appropriate error message.

      2. Make pipeline invalid.

    2. If descriptor.layout is undefined:

      1. Set pipeline.[[layout]] to a new default pipeline layout for pipeline.

      Otherwise set pipeline.[[layout]] to descriptor.layout.

  3. Return pipeline.

createComputePipelineAsync(descriptor)

Creates a GPUComputePipeline. The returned Promise resolves when the created pipeline is ready to be used without additional delay.

If pipeline creation fails, the returned Promise rejects with an OperationError.

Note: Use of this method is preferred whenever possible, as it prevents blocking the queue timeline work on pipeline compilation.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createComputePipelineAsync(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUComputePipelineDescriptor Description of the GPUComputePipeline to create.

Returns: Promise<GPUComputePipeline>

  1. Let promise be a new promise.

  2. Issue the following steps on the Device timeline of this:

    1. Let pipeline be a new GPUComputePipeline created as if this.createComputePipeline() was called with descriptor;

    2. When pipeline is ready to be used, resolve promise with pipeline.

  3. Return promise.

10.3. GPURenderPipeline

A GPURenderPipeline is a kind of pipeline that controls the vertex and fragment shader stages, and can be used in GPURenderPassEncoder as well as GPURenderBundleEncoder.

Render pipeline inputs are:

Render pipeline outputs are:

A render pipeline is comprised of the following render stages:

  1. Vertex fetch, controlled by GPUVertexState.buffers

  2. Vertex shader, controlled by GPUVertexState

  3. Primitive assembly, controlled by GPUPrimitiveState

  4. Rasterization, controlled by GPUPrimitiveState, GPUDepthStencilState, and GPUMultisampleState

  5. Fragment shader, controlled by GPUFragmentState

  6. Stencil test and operation, controlled by GPUDepthStencilState

  7. Depth test and write, controlled by GPUDepthStencilState

  8. Output merging, controlled by GPUFragmentState.targets

[Exposed=(Window, DedicatedWorker), SecureContext]
interface GPURenderPipeline {
};
GPURenderPipeline includes GPUObjectBase;
GPURenderPipeline includes GPUPipelineBase;

GPURenderPipeline has the following internal slots:

[[descriptor]], of type GPURenderPipelineDescriptor

The GPURenderPipelineDescriptor describing this pipeline.

All optional fields of GPURenderPipelineDescriptor are defined.

[[strip_index_format]], of type GPUIndexFormat?

The format index data this pipeline requires if using a strip primitive topology, initially undefined.

[[writesDepth]], of type boolean

True if the pipeline writes to the depth component of the depth/stencil attachment

[[writesStencil]], of type boolean

True if the pipeline writes to the stencil component of the depth/stencil attachment

10.3.1. Creation

dictionary GPURenderPipelineDescriptor : GPUPipelineDescriptorBase {
    required GPUVertexState vertex;
    GPUPrimitiveState primitive = {};
    GPUDepthStencilState depthStencil;
    GPUMultisampleState multisample = {};
    GPUFragmentState fragment;
};

A GPURenderPipelineDescriptor describes the state of a render pipeline by configuring each of the render stages. See § 21.3 Rendering for the details.

createRenderPipeline(descriptor)

Creates a GPURenderPipeline.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createRenderPipeline(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPURenderPipelineDescriptor Description of the GPURenderPipeline to create.

Returns: GPURenderPipeline

  1. Let pipeline be a new valid GPURenderPipeline object.

  2. Issue the following steps on the Device timeline of this:

    1. If any of the following conditions are unsatisfied:

      Then:

      1. Generate a GPUValidationError in the current scope with appropriate error message.

      2. Make pipeline invalid.

    2. Set pipeline.[[descriptor]] to descriptor.

    3. Set pipeline.[[strip_index_format]] to descriptor.primitive.stripIndexFormat.

    4. Set pipeline.[[writesDepth]] to false.

    5. Set pipeline.[[writesStencil]] to false.

    6. Let depthStencil be descriptor.depthStencil.

    7. If depthStencil is not null:

      1. Set pipeline.[[writesDepth]] to depthStencil.depthWriteEnabled.

      2. If depthStencil.stencilWriteMask is not 0:

        1. Let stencilFront be depthStencil.stencilFront.

        2. Let stencilBack be depthStencil.stencilBack.

        3. Let cullMode be descriptor.primitive.cullMode.

        4. If cullMode is not "front", and any of stencilFront.passOp, stencilFront.depthFailOp, or stencilFront.failOp is not "keep":

          1. Set pipeline.[[writesStencil]] to true.

        5. If cullMode is not "back", and any of stencilBack.passOp, stencilBack.depthFailOp, or stencilBack.failOp is not "keep":

          1. Set pipeline.[[writesStencil]] to true.

    8. If descriptor.layout is undefined:

      1. Set pipeline.[[layout]] to a new default pipeline layout for pipeline.

      Otherwise set pipeline.[[layout]] to descriptor.layout.

  3. Return pipeline.

need description of the render states.

createRenderPipelineAsync(descriptor)

Creates a GPURenderPipeline. The returned Promise resolves when the created pipeline is ready to be used without additional delay.

If pipeline creation fails, the returned Promise rejects with an OperationError.

Note: Use of this method is preferred whenever possible, as it prevents blocking the queue timeline work on pipeline compilation.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createRenderPipelineAsync(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPURenderPipelineDescriptor Description of the GPURenderPipeline to create.

Returns: Promise<GPURenderPipeline>

  1. Let promise be a new promise.

  2. Issue the following steps on the Device timeline of this:

    1. Let pipeline be a new GPURenderPipeline created as if this.createRenderPipeline() was called with descriptor;

    2. When pipeline is ready to be used, resolve promise with pipeline.

  3. Return promise.

validating GPURenderPipelineDescriptor(descriptor, device) Arguments:

Return true if all of the following conditions are satisfied:

should we validate that cullMode is none for points and lines?

define what "compatible" means for render target formats.

need a proper limit for the maximum number of color targets.

10.3.2. Primitive State

enum GPUPrimitiveTopology {
    "point-list",
    "line-list",
    "line-strip",
    "triangle-list",
    "triangle-strip"
};
dictionary GPUPrimitiveState {
    GPUPrimitiveTopology topology = "triangle-list";
    GPUIndexFormat stripIndexFormat;
    GPUFrontFace frontFace = "ccw";
    GPUCullMode cullMode = "none";

    // Enable depth clamping (requires "depth-clamping" feature)
    boolean clampDepth = false;
};
validating GPUPrimitiveState(descriptor, features) Arguments:

Return true if all of the following conditions are satisfied:

enum GPUFrontFace {
    "ccw",
    "cw"
};
enum GPUCullMode {
    "none",
    "front",
    "back"
};

10.3.3. Multisample State

dictionary GPUMultisampleState {
    GPUSize32 count = 1;
    GPUSampleMask mask = 0xFFFFFFFF;
    boolean alphaToCoverageEnabled = false;
};
validating GPUMultisampleState(descriptor) Arguments:

Return true if all of the following conditions are satisfied:

10.3.4. Fragment State

dictionary GPUFragmentState: GPUProgrammableStage {
    required sequence<GPUColorTargetState> targets;
};
validating GPUFragmentState(descriptor) Return true if all of the following requirements are met:
component is a valid GPUBlendComponent if it meets the following requirements:

define the area of reach for "statically used" things of GPUProgrammableStage

10.3.5. Color Target State

dictionary GPUColorTargetState {
    required GPUTextureFormat format;

    GPUBlendState blend;
    GPUColorWriteFlags writeMask = 0xF;  // GPUColorWrite.ALL
};
dictionary GPUBlendState {
    required GPUBlendComponent color;
    required GPUBlendComponent alpha;
};
typedef [EnforceRange] unsigned long GPUColorWriteFlags;
[Exposed=(Window, DedicatedWorker)]
namespace GPUColorWrite {
    const GPUFlagsConstant RED   = 0x1;
    const GPUFlagsConstant GREEN = 0x2;
    const GPUFlagsConstant BLUE  = 0x4;
    const GPUFlagsConstant ALPHA = 0x8;
    const GPUFlagsConstant ALL   = 0xF;
};
10.3.5.1. Blend State
dictionary GPUBlendComponent {
    GPUBlendOperation operation = "add";
    GPUBlendFactor srcFactor = "one";
    GPUBlendFactor dstFactor = "zero";
};
enum GPUBlendFactor {
    "zero",
    "one",
    "src",
    "one-minus-src",
    "src-alpha",
    "one-minus-src-alpha",
    "dst",
    "one-minus-dst",
    "dst-alpha",
    "one-minus-dst-alpha",
    "src-alpha-saturated",
    "constant",
    "one-minus-constant"
};
enum GPUBlendOperation {
    "add",
    "subtract",
    "reverse-subtract",
    "min",
    "max"
};

10.3.6. Depth/Stencil State

dictionary GPUDepthStencilState {
    required GPUTextureFormat format;

    boolean depthWriteEnabled = false;
    GPUCompareFunction depthCompare = "always";

    GPUStencilFaceState stencilFront = {};
    GPUStencilFaceState stencilBack = {};

    GPUStencilValue stencilReadMask = 0xFFFFFFFF;
    GPUStencilValue stencilWriteMask = 0xFFFFFFFF;

    GPUDepthBias depthBias = 0;
    float depthBiasSlopeScale = 0;
    float depthBiasClamp = 0;
};
dictionary GPUStencilFaceState {
    GPUCompareFunction compare = "always";
    GPUStencilOperation failOp = "keep";
    GPUStencilOperation depthFailOp = "keep";
    GPUStencilOperation passOp = "keep";
};
enum GPUStencilOperation {
    "keep",
    "zero",
    "replace",
    "invert",
    "increment-clamp",
    "decrement-clamp",
    "increment-wrap",
    "decrement-wrap"
};
validating GPUDepthStencilState(descriptor) Arguments:

Return true, if and only if, all of the following conditions are satisfied:

how can this algorithm support depth/stencil formats that are added in extensions?

10.3.7. Vertex State

enum GPUIndexFormat {
    "uint16",
    "uint32"
};

The index format determines both the data type of index values in a buffer and, when used with strip primitive topologies ("line-strip" or "triangle-strip") also specifies the primitive restart value. The primitive restart value indicates which index value indicates that a new primitive should be started rather than continuing to construct the triangle strip with the prior indexed vertices.

GPUPrimitiveStates that specify a strip primitive topology must specify a stripIndexFormat so that the primitive restart value that will be used is known at pipeline creation time. GPUPrimitiveStates that specify a list primitive topology must set stripIndexFormat to undefined, and will use the index format passed to setIndexBuffer() when rendering.

Index format Byte size Primitive restart value
"uint16" 2 0xFFFF
"uint32" 4 0xFFFFFFFF
10.3.7.1. Vertex Formats

The name of the format specifies the order of components, bits per component, and vertex data type for the component.

enum GPUVertexFormat {
    "uint8x2",
    "uint8x4",
    "sint8x2",
    "sint8x4",
    "unorm8x2",
    "unorm8x4",
    "snorm8x2",
    "snorm8x4",
    "uint16x2",
    "uint16x4",
    "sint16x2",
    "sint16x4",
    "unorm16x2",
    "unorm16x4",
    "snorm16x2",
    "snorm16x4",
    "float16x2",
    "float16x4",
    "float32",
    "float32x2",
    "float32x3",
    "float32x4",
    "uint32",
    "uint32x2",
    "uint32x3",
    "uint32x4",
    "sint32",
    "sint32x2",
    "sint32x3",
    "sint32x4",
};

The multi-component formats specify the number of components after "x". As such, "sint32x3" denotes a 3-component vector of i32 values in the shader.

enum GPUVertexStepMode {
    "vertex",
    "instance"
};

The step mode configures how an address for vertex buffer data is computed, based on the current vertex or instance index:

"vertex"

The address is advanced by arrayStride for each vertex, and reset between instances.

"instance"

The address is advanced by arrayStride for each instance.

dictionary GPUVertexState: GPUProgrammableStage {
    sequence<GPUVertexBufferLayout?> buffers = [];
};

A vertex buffer is, conceptually, a view into buffer memory as an array of structures. arrayStride is the stride, in bytes, between elements of that array. Each element of a vertex buffer is like a structure with a memory layout defined by its attributes, which describe the members of the structure.

Each GPUVertexAttribute describes its format and its offset, in bytes, within the structure.

Each attribute appears as a separate input in a vertex shader, each bound by a numeric location, which is specified by shaderLocation. Every location must be unique within the GPUVertexState.

dictionary GPUVertexBufferLayout {
    required GPUSize64 arrayStride;
    GPUVertexStepMode stepMode = "vertex";
    required sequence<GPUVertexAttribute> attributes;
};
dictionary GPUVertexAttribute {
    required GPUVertexFormat format;
    required GPUSize64 offset;

    required GPUIndex32 shaderLocation;
};
validating GPUVertexBufferLayout(device, descriptor, vertexStage) Arguments:

Return true, if and only if, all of the following conditions are satisfied:

validating GPUVertexState(device, descriptor) Arguments:

Return true, if and only if, all of the following conditions are satisfied:

11. Command Buffers

Command buffers are pre-recorded lists of GPU commands that can be submitted to a GPUQueue for execution. Each GPU command represents a task to be performed on the GPU, such as setting state, drawing, copying resources, etc.

11.1. GPUCommandBuffer

[Exposed=(Window, DedicatedWorker), SecureContext]
interface GPUCommandBuffer {
    readonly attribute Promise<double> executionTime;
};
GPUCommandBuffer includes GPUObjectBase;

GPUCommandBuffer has the following attributes:

executionTime, of type Promise<double>, readonly

The total time, in seconds, that the GPU took to execute this command buffer.

Note: If measureExecutionTime is true, this resolves after the command buffer executes. Otherwise, this rejects with an OperationError.

Specify the creation and resolution of the promise.

In finish(), it should be specified that a new promise is created and stored in this attribute. The promise starts rejected if measureExecutionTime is false. If the finish() fails, then the promise resolves to 0.

In submit(), it should be specified that (if measureExecutionTime is set), work is issued to read back the execution time, and, when that completes, the promise is resolved with that value. If the submit() fails, then the promise resolves to 0.

GPUCommandBuffer has the following internal slots:

[[command_list]] of type list<GPU command>.

A list of GPU commands to be executed on the Queue timeline when this command buffer is submitted.

11.1.1. Creation

dictionary GPUCommandBufferDescriptor : GPUObjectDescriptorBase {
};

12. Command Encoding

12.1. GPUCommandEncoder

[Exposed=(Window, DedicatedWorker), SecureContext]
interface GPUCommandEncoder {
    GPURenderPassEncoder beginRenderPass(GPURenderPassDescriptor descriptor);
    GPUComputePassEncoder beginComputePass(optional GPUComputePassDescriptor descriptor = {});

    undefined copyBufferToBuffer(
        GPUBuffer source,
        GPUSize64 sourceOffset,
        GPUBuffer destination,
        GPUSize64 destinationOffset,
        GPUSize64 size);

    undefined copyBufferToTexture(
        GPUImageCopyBuffer source,
        GPUImageCopyTexture destination,
        GPUExtent3D copySize);

    undefined copyTextureToBuffer(
        GPUImageCopyTexture source,
        GPUImageCopyBuffer destination,
        GPUExtent3D copySize);

    undefined copyTextureToTexture(
        GPUImageCopyTexture source,
        GPUImageCopyTexture destination,
        GPUExtent3D copySize);

    undefined pushDebugGroup(USVString groupLabel);
    undefined popDebugGroup();
    undefined insertDebugMarker(USVString markerLabel);

    undefined writeTimestamp(GPUQuerySet querySet, GPUSize32 queryIndex);

    undefined resolveQuerySet(
        GPUQuerySet querySet,
        GPUSize32 firstQuery,
        GPUSize32 queryCount,
        GPUBuffer destination,
        GPUSize64 destinationOffset);

    GPUCommandBuffer finish(optional GPUCommandBufferDescriptor descriptor = {});
};
GPUCommandEncoder includes GPUObjectBase;

GPUCommandEncoder has the following internal slots:

[[command_list]] of type list<GPU command>.

A list of GPU command to be executed on the Queue timeline when the GPUCommandBuffer this encoder produces is submitted.

[[state]] of type encoder state.

The current state of the GPUCommandEncoder, initially set to open.

[[debug_group_stack]] of type stack<USVString>.

A stack of active debug group labels.

Each GPUCommandEncoder has a current encoder state on the Content timeline which may be one of the following:

"open"

Indicates the GPUCommandEncoder is available to begin new operations. The [[state]] is open any time the GPUCommandEncoder is valid and has no active GPURenderPassEncoder or GPUComputePassEncoder.

"encoding a render pass"

Indicates the GPUCommandEncoder has an active GPURenderPassEncoder. The [[state]] becomes encoding a render pass once beginRenderPass() is called sucessfully until endPass() is called on the returned GPURenderPassEncoder, at which point the [[state]] (if the encoder is still valid) reverts to open.

"encoding a compute pass"

Indicates the GPUCommandEncoder has an active GPUComputePassEncoder. The [[state]] becomes encoding a compute pass once beginComputePass() is called sucessfully until endPass() is called on the returned GPUComputePassEncoder, at which point the [[state]] (if the encoder is still valid) reverts to open.

"closed"

Indicates the GPUCommandEncoder is no longer available for any operations. The [[state]] becomes closed once finish() is called or the GPUCommandEncoder otherwise becomes invalid.

12.1.1. Creation

dictionary GPUCommandEncoderDescriptor : GPUObjectDescriptorBase {
    boolean measureExecutionTime = false;
};
measureExecutionTime, of type boolean, defaulting to false

Enable measurement of the GPU execution time of the entire command buffer.

createCommandEncoder(descriptor)

Creates a GPUCommandEncoder.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createCommandEncoder(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUCommandEncoderDescriptor Description of the GPUCommandEncoder to create.

Returns: GPUCommandEncoder

Describe createCommandEncoder() algorithm steps.

12.2. Pass Encoding

beginRenderPass(descriptor)

Begins encoding a render pass described by descriptor.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.beginRenderPass(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPURenderPassDescriptor Description of the GPURenderPassEncoder to create.

Returns: GPURenderPassEncoder

Issue the following steps on the Device timeline of this:

  1. Let pass be a new GPURenderPassEncoder object.

  2. If any of the following conditions are unsatisfied, generate a validation error and stop.

  3. Set this.[[state]] to encoding a render pass.

  4. For each colorAttachment in descriptor.colorAttachments:

    1. The texture subresource seen by colorAttachment.view is considered to be used as attachment for the duration of the render pass.

  5. Let depthStencilAttachment be descriptor.depthStencilAttachment.

  6. If depthStencilAttachment is not null:

    1. Let depthStencilView be depthStencilAttachment.view.

    2. If depthStencilAttachment.depthReadOnly and stencilReadOnly are set:

      1. The texture subresources seen by depthStencilView are considered to be used as attachment-read for the duration of the render pass.

    3. Else, the texture subresource seen by depthStencilView is considered to be used as attachment for the duration of the render pass.

    4. Set pass.[[depthReadOnly]] to depthStencilAttachment.depthReadOnly.

    5. Set pass.[[stencilReadOnly]] to depthStencilAttachment.stencilReadOnly.

  7. Set pass.[[layout]] to derive render targets layout from pass(descriptor).

  8. Return pass.

specify the behavior of read-only depth/stencil Issue: Enqueue attachment loads (with loadOp clear).

beginComputePass(descriptor)

Begins encoding a compute pass described by descriptor.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.beginComputePass(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUComputePassDescriptor

Returns: GPUComputePassEncoder

Issue the following steps on the Device timeline of this:

  1. If any of the following conditions are unsatisfied, generate a validation error and stop.

  2. Set this.[[state]] to encoding a compute pass.

  3. Let pass be a new GPUComputePassEncoder object.

  4. Return pass.

12.3. Copy Commands

these dictionary definitions should be inside the image copies section.

12.3.1. GPUImageDataLayout

dictionary GPUImageDataLayout {
    GPUSize64 offset = 0;
    GPUSize32 bytesPerRow;
    GPUSize32 rowsPerImage;
};

A GPUImageDataLayout is a layout of images within some linear memory. It’s used when copying data between a texture and a buffer, or when scheduling a write into a texture from the GPUQueue.

Operations that copy between byte arrays and textures always work with rows of texel blocks, which we’ll call block rows. It’s not possible to update only a part of a texel block.

Define images more precisely. In particular, define them as being comprised of texel blocks.

Define the exact copy semantics, by reference to common algorithms shared by the copy methods.

bytesPerRow, of type GPUSize32

The stride, in bytes, between the beginning of each block row and the subsequent block row.

Required if there are multiple block rows (i.e. the height or depth is more than one block).

rowsPerImage, of type GPUSize32

Number of block rows per single image of the texture. rowsPerImage × bytesPerRow is the stride, in bytes, between the beginning of each image of data and the subsequent image.

Required if there are multiple images (i.e. the depth is more than one).

12.3.2. GPUImageCopyBuffer

In an image copy operation, GPUImageCopyBuffer defines a GPUBuffer and, together with the copySize, how image data is laid out in the buffer’s memory (see GPUImageDataLayout).

dictionary GPUImageCopyBuffer : GPUImageDataLayout {
    required GPUBuffer buffer;
};
validating GPUImageCopyBuffer

Arguments:

Returns: boolean

Return true if and only if all of the following conditions are satisfied:

12.3.3. GPUImageCopyTexture

In an image copy operation, a GPUImageCopyTexture defines a GPUTexture and, together with the copySize, the sub-region of the texture (spanning one or more contiguous texture subresources at the same mip-map level).

dictionary GPUImageCopyTexture {
    required GPUTexture texture;
    GPUIntegerCoordinate mipLevel = 0;
    GPUOrigin3D origin = {};
    GPUTextureAspect aspect = "all";
};
texture, of type GPUTexture

Texture to copy to/from.

mipLevel, of type GPUIntegerCoordinate, defaulting to 0

Mip-map level of the texture to copy to/from.

origin, of type GPUOrigin3D, defaulting to {}

Defines the origin of the copy - the minimum corner of the texture sub-region to copy to/from. Together with copySize, defines the full copy sub-region.

aspect, of type GPUTextureAspect, defaulting to "all"

Defines which aspects of the texture to copy to/from.

validating GPUImageCopyTexture

Arguments:

Returns: boolean

Let:

Return true if and only if all of the following conditions apply:

Define the copies with 1d and 3d textures. [Issue #gpuweb/gpuweb#69]

12.3.4. GPUImageCopyTextureTagged

WebGPU textures hold raw numeric data, and are not tagged with semantic metadata describing colors. However, copyExternalImageToTexture() copies from sources that describe colors.

A GPUImageCopyTextureTagged is a GPUImageCopyTexture which is additionally tagged with color space/encoding and alpha-premultiplication metadata, so that semantic color data may be preserved during copies. This metadata only affects the semantics of the copyExternalImageToTexture() call.

dictionary GPUImageCopyTextureTagged : GPUImageCopyTexture {
    GPUPredefinedColorSpace colorSpace = "srgb";
    boolean premultipliedAlpha = false;
};
colorSpace, of type GPUPredefinedColorSpace, defaulting to "srgb"

Describes the color space and encoding used to encode data into the destination texture.

Note: If colorSpace matches the source image, no conversion occurs. ImageBitmap color space tagging and conversion can be controlled via ImageBitmapOptions.

premultipliedAlpha, of type boolean, defaulting to false

Describes whether the data written into the texture should be have its RGB channels premultiplied by the alpha channel, or not.

If this option is set to true and the source is also premultiplied, the source RGB values must be preserved even if they exceed their corresponding alpha values.

Note: If premultipliedAlpha matches the source image, no conversion occurs. 2d canvases are always premultiplied, while WebGL canvases can be controlled via WebGLContextAttributes. ImageBitmap premultiplication can be controlled via ImageBitmapOptions.

Define (and test) the encoding of color values into the various encodings allowed by copyExternalImageToTexture().

12.3.5. GPUImageCopyExternalImage

dictionary GPUImageCopyExternalImage {
    required (ImageBitmap or HTMLCanvasElement or OffscreenCanvas) source;
    GPUOrigin2D origin = {};
};

GPUImageCopyExternalImage has the following members:

source, of type (ImageBitmap or HTMLCanvasElement or OffscreenCanvas)

The source of the image copy. The copy source data is captured at the moment that copyExternalImageToTexture() is issued.

origin, of type GPUOrigin2D, defaulting to {}

Defines the origin of the copy - the minimum corner of the source sub-region to copy from. Together with copySize, defines the full copy sub-region.

12.3.6. Buffer Copies

copyBufferToBuffer(source, sourceOffset, destination, destinationOffset, size)

Encode a command into the GPUCommandEncoder that copies data from a sub-region of a GPUBuffer to a sub-region of another GPUBuffer.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.copyBufferToBuffer(source, sourceOffset, destination, destinationOffset, size) method.
Parameter Type Nullable Optional Description
source GPUBuffer The GPUBuffer to copy from.
sourceOffset GPUSize64 Offset in bytes into source to begin copying from.
destination GPUBuffer The GPUBuffer to copy to.
destinationOffset GPUSize64 Offset in bytes into destination to place the copied data.
size GPUSize64 Bytes to copy.

Returns: undefined

If any of the following conditions are unsatisfied, generate a validation error and stop.

Define the state machine for GPUCommandEncoder. [Issue #gpuweb/gpuweb#21]

figure out how to handle overflows in the spec. [Issue #gpuweb/gpuweb#69]

12.3.7. Image Copies

WebGPU provides copyBufferToTexture() for buffer-to-texture copies and copyTextureToBuffer() for texture-to-buffer copies.

The following definitions and validation rules apply to both copyBufferToTexture() and copyTextureToBuffer().

imageCopyTexture subresource size and Valid Texture Copy Range also applies to copyTextureToTexture().

imageCopyTexture subresource size

Arguments:

Returns: GPUExtent3D

The imageCopyTexture subresource size of imageCopyTexture is calculated as follows:

Its width, height and depthOrArrayLayers are the width, height, and depth, respectively, of the physical size of imageCopyTexture.texture subresource at mipmap level imageCopyTexture.mipLevel.

define this as an algorithm with (texture, mipmapLevel) parameters and use the call syntax instead of referring to the definition by label.

validating linear texture data(layout, byteSize, format, copyExtent)

Arguments:

GPUImageDataLayout layout

Layout of the linear texture data.

GPUSize64 byteSize

Total size of the linear data, in bytes.

GPUTextureFormat format

Format of the texture.

GPUExtent3D copyExtent

Extent of the texture to copy.

  1. Let blockWidth, blockHeight, and blockSize be the texel block width, height, and size of format.

  2. It is assumed that copyExtent.width is a multiple of blockWidth and copyExtent.height is a multiple of blockHeight. Let:

    • widthInBlocks be copyExtent.width ÷ blockWidth.

    • heightInBlocks be copyExtent.height ÷ blockHeight.

    • bytesInLastRow be blockSize × widthInBlocks.

  3. Fail if the following conditions are not satisfied:

  4. Let requiredBytesInCopy be 0.

  5. If copyExtent.depthOrArrayLayers > 1:

    1. Let bytesPerImage be layout.bytesPerRow × layout.rowsPerImage.

    2. Let bytesBeforeLastImage be bytesPerImage × (copyExtent.depthOrArrayLayers − 1).

    3. Add bytesBeforeLastImage to requiredBytesInCopy.

  6. If copyExtent.depthOrArrayLayers > 0:

    1. If heightInBlocks > 1, add layout.bytesPerRow × (heightInBlocks − 1) to requiredBytesInCopy.

    2. If heightInBlocks > 0, add bytesInLastRow to requiredBytesInCopy.

  7. Fail if the following conditions are not satisfied:

    • layout.offset + requiredBytesInCopybyteSize.

Valid Texture Copy Range

Given a GPUImageCopyTexture imageCopyTexture and a GPUExtent3D copySize, let

The following validation rules apply:

Define the copies with 1d and 3d textures. [Issue #gpuweb/gpuweb#69]

Additional restrictions on rowsPerImage if needed. [Issue #gpuweb/gpuweb#537]

Define the copies with "depth24plus", "depth24plus-stencil8", and "stencil8". [Issue #gpuweb/gpuweb#652]

convert "Valid Texture Copy Range" into an algorithm with parameters, similar to "validating linear texture data"

copyBufferToTexture(source, destination, copySize)

Encode a command into the GPUCommandEncoder that copies data from a sub-region of a GPUBuffer to a sub-region of one or multiple continuous texture subresources.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.copyBufferToTexture(source, destination, copySize) method.
Parameter Type Nullable Optional Description
source GPUImageCopyBuffer Combined with copySize, defines the region of the source buffer.
destination GPUImageCopyTexture Combined with copySize, defines the region of the destination texture subresource.
copySize GPUExtent3D

Returns: undefined

If any of the following conditions are unsatisfied, generate a validation error and stop.

copyTextureToBuffer(source, destination, copySize)

Encode a command into the GPUCommandEncoder that copies data from a sub-region of one or multiple continuous texture subresourcesto a sub-region of a GPUBuffer.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.copyTextureToBuffer(source, destination, copySize) method.
Parameter Type Nullable Optional Description
source GPUImageCopyTexture Combined with copySize, defines the region of the source texture subresources.
destination GPUImageCopyBuffer Combined with copySize, defines the region of the destination buffer.
copySize GPUExtent3D

Returns: undefined

If any of the following conditions are unsatisfied, generate a validation error and stop.

copyTextureToTexture(source, destination, copySize)

Encode a command into the GPUCommandEncoder that copies data from a sub-region of one or multiple contiguous texture subresources to another sub-region of one or multiple continuous texture subresources.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.copyTextureToTexture(source, destination, copySize) method.
Parameter Type Nullable Optional Description
source GPUImageCopyTexture Combined with copySize, defines the region of the source texture subresources.
destination GPUImageCopyTexture Combined with copySize, defines the region of the destination texture subresources.
copySize GPUExtent3D

Returns: undefined

  1. If any of the following conditions are unsatisfied, generate a validation error and stop.

The set of subresources for texture copy(imageCopyTexture, copySize) is the set containing:

12.4. Debug Markers

Both command encoders and programmable pass encoders provide methods to apply debug labels to groups of commands or insert a single label into the command sequence. Debug groups can be nested to create a hierarchy of labeled commands. These labels may be passed to the native API backends for tooling, may be used by the user agent’s internal tooling, or may be a no-op when such tooling is not available or applicable.

Debug groups in a GPUCommandEncoder or GPUProgrammablePassEncoder must be well nested.

pushDebugGroup(groupLabel)

Marks the beginning of a labeled group of commands for the GPUCommandEncoder.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.pushDebugGroup(groupLabel) method.
Parameter Type Nullable Optional Description
groupLabel USVString The label for the command group.

Returns: undefined

Issue the following steps on the Device timeline of this:

popDebugGroup()

Marks the end of a labeled group of commands for the GPUCommandEncoder.

Called on: GPUCommandEncoder this.

Returns: undefined

Issue the following steps on the Device timeline of this:

insertDebugMarker(markerLabel)

Marks a point in a stream of commands with a label string.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.insertDebugMarker(markerLabel) method.
Parameter Type Nullable Optional Description
markerLabel USVString The label to insert.

Returns: undefined

Issue the following steps on the Device timeline of this:

  • If any of the following conditions are unsatisfied, make this invalid and stop.

12.5. Queries

writeTimestamp(querySet, queryIndex)

Writes a timestamp value into querySet when all previous commands have completed executing.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.writeTimestamp(querySet, queryIndex) method.
Parameter Type Nullable Optional Description
querySet GPUQuerySet The query set that will store the timestamp values.
queryIndex GPUSize32 The index of the query in the query set.

Returns: undefined

  1. If this.[[device]].[[features]] does not contain "timestamp-query", throw a TypeError.

  2. If any of the following conditions are unsatisfied, generate a validation error and stop.

Describe writeTimestamp() algorithm steps.

resolveQuerySet(querySet, firstQuery, queryCount, destination, destinationOffset)
Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.resolveQuerySet(querySet, firstQuery, queryCount, destination, destinationOffset) method.
Parameter Type Nullable Optional Description
querySet GPUQuerySet
firstQuery GPUSize32
queryCount GPUSize32
destination GPUBuffer
destinationOffset GPUSize64

Returns: undefined

If any of the following conditions are unsatisfied, generate a GPUValidationError and stop.

  • this.[[state]] is open.

  • querySet is valid to use with this.

  • destination is valid to use with this.

  • destination.[[usage]] contains QUERY_RESOLVE.

  • firstQuery is less than the number of queries in querySet.

  • (firstQuery + queryCount) is less than or equal to the number of queries in querySet.

  • destinationOffset is a multiple of 256.

  • destinationOffset + 8 × queryCountdestination.[[size]].

Describe resolveQuerySet() algorithm steps.

12.6. Finalization

A GPUCommandBuffer containing the commands recorded by the GPUCommandEncoder can be created by calling finish(). Once finish() has been called the command encoder can no longer be used.

finish(descriptor)

Completes recording of the commands sequence and returns a corresponding GPUCommandBuffer.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.finish(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUCommandBufferDescriptor

Returns: GPUCommandBuffer

  1. Let commandBuffer be a new GPUCommandBuffer.

  2. Issue the following steps on the Device timeline of this:

    1. If any of the following conditions are unsatisfied, generate a validation error and stop.

    2. Set this.[[state]] to closed.

    3. Let commandBuffer.[[command_list]] be a clone of this.[[command_list]].

  3. Return commandBuffer.

13. Programmable Passes

interface mixin GPUProgrammablePassEncoder {
    undefined setBindGroup(GPUIndex32 index, GPUBindGroup bindGroup,
                      optional sequence<GPUBufferDynamicOffset> dynamicOffsets = []);

    undefined setBindGroup(GPUIndex32 index, GPUBindGroup bindGroup,
                      Uint32Array dynamicOffsetsData,
                      GPUSize64 dynamicOffsetsDataStart,
                      GPUSize32 dynamicOffsetsDataLength);

    undefined pushDebugGroup(USVString groupLabel);
    undefined popDebugGroup();
    undefined insertDebugMarker(USVString markerLabel);
};

GPUProgrammablePassEncoder has the following internal slots:

[[command_encoder]] of type GPUCommandEncoder.

The GPUCommandEncoder that created this programmable pass.

[[debug_group_stack]] of type stack<USVString>.

A stack of active debug group labels.

[[bind_groups]], of type ordered map<GPUIndex32, GPUBindGroup>

The current GPUBindGroup for each index, initially empty.

13.1. Bind Groups

setBindGroup(index, bindGroup, dynamicOffsets)

Sets the current GPUBindGroup for the given index.

Called on: GPUProgrammablePassEncoder this.

Arguments:

Arguments for the GPUProgrammablePassEncoder.setBindGroup(index, bindGroup, dynamicOffsets) method.
Parameter Type Nullable Optional Description
index GPUIndex32 The index to set the bind group at.
bindGroup GPUBindGroup Bind group to use for subsequent render or compute commands.

Resolve bikeshed conflict when using argumentdef with overloaded functions that prevents us from defining dynamicOffsets.

Returns: undefined

Issue the following steps on the Device timeline of this.[[device]]:

  1. If any of the following conditions are unsatisfied, make this invalid and stop.

  2. Set this.[[bind_groups]][index] to be bindGroup.

setBindGroup(index, bindGroup, dynamicOffsetsData, dynamicOffsetsDataStart, dynamicOffsetsDataLength)

Sets the current GPUBindGroup for the given index, specifying dynamic offsets as a subset of a Uint32Array.

Called on: GPUProgrammablePassEncoder this.

Arguments:

Arguments for the GPUProgrammablePassEncoder.setBindGroup(index, bindGroup, dynamicOffsetsData, dynamicOffsetsDataStart, dynamicOffsetsDataLength) method.
Parameter Type Nullable Optional Description
index GPUIndex32 The index to set the bind group at.
bindGroup GPUBindGroup Bind group to use for subsequent render or compute commands.
dynamicOffsetsData Uint32Array Array containing buffer offsets in bytes for each entry in bindGroup marked as buffer.hasDynamicOffset.
dynamicOffsetsDataStart GPUSize64 Offset in elements into dynamicOffsetsData where the buffer offset data begins.
dynamicOffsetsDataLength GPUSize32 Number of buffer offsets to read from dynamicOffsetsData.

Returns: undefined

  1. If any of the following requirements are unmet, throw a RangeError and stop.

    • dynamicOffsetsDataStart must be ≥ 0.

    • dynamicOffsetsDataStart + dynamicOffsetsDataLength must be ≤ dynamicOffsetsData.length.

  2. Let dynamicOffsets be a list containing the range, starting at index dynamicOffsetsDataStart, of dynamicOffsetsDataLength elements of a copy of dynamicOffsetsData.

  3. Call this.setBindGroup(index, bindGroup, dynamicOffsets).

To Iterate over each dynamic binding offset in a given GPUBindGroup bindGroup with a given list of steps to be executed for each dynamic offset:
  1. Let dynamicOffsetIndex be 0.

  2. Let layout be bindGroup.[[layout]].

  3. For each GPUBindGroupEntry entry in bindGroup.[[entries]]:

    1. Let bindingDescriptor be the GPUBindGroupLayoutEntry at layout.[[entryMap]][entry.binding]:

    2. If bindingDescriptor.buffer is not undefined and bindingDescriptor.buffer.hasDynamicOffset is true:

      1. Let bufferBinding be entry.resource.

      2. Let bufferLayout be bindingDescriptor.buffer.

      3. Call steps with bufferBinding, bufferLayout, and dynamicOffsetIndex.

      4. Let dynamicOffsetIndex be dynamicOffsetIndex + 1

Validate encoder bind groups(encoder, pipeline)

Arguments:

GPUProgrammablePassEncoder encoder

Encoder who’s bind groups are being validated.

GPUPipelineBase pipeline

Pipline to validate encoders bind groups are compatible with.

If any of the following conditions are unsatisfied, return false:

Check buffer bindings against minBindingSize if present.

Otherwise return true.

13.2. Debug Markers

Debug marker methods for programmable pass encoders provide the same functionality as command encoder debug markers while recording a programmable pass.

pushDebugGroup(groupLabel)

Marks the beginning of a labeled group of commands for the GPUProgrammablePassEncoder.

Called on: GPUProgrammablePassEncoder this.

Arguments:

Arguments for the GPUProgrammablePassEncoder.pushDebugGroup(groupLabel) method.
Parameter Type Nullable Optional Description
groupLabel USVString The label for the command group.

Returns: undefined

Issue the following steps on the Device timeline of this:

  1. Push groupLabel onto this.[[debug_group_stack]].

popDebugGroup()

Marks the end of a labeled group of commands for the GPUProgrammablePassEncoder.

Called on: GPUProgrammablePassEncoder this.

Returns: undefined

Issue the following steps on the Device timeline of this:

  1. If any of the following conditions are unsatisfied, generate a validation error and stop.

  2. Pop an entry off of this.[[debug_group_stack]].

insertDebugMarker(markerLabel)

Inserts a single debug marker label into the GPUProgrammablePassEncoder's commands sequence.

Called on: GPUProgrammablePassEncoder this.

Arguments:

Arguments for the GPUProgrammablePassEncoder.insertDebugMarker(markerLabel) method.
Parameter Type Nullable Optional Description
markerLabel USVString The label to insert.

Returns: undefined

14. Compute Passes

14.1. GPUComputePassEncoder

[Exposed=(Window, DedicatedWorker), SecureContext]
interface GPUComputePassEncoder {
    undefined setPipeline(GPUComputePipeline pipeline);
    undefined dispatch(GPUSize32 x, optional GPUSize32 y = 1, optional GPUSize32 z = 1);
    undefined dispatchIndirect(GPUBuffer indirectBuffer, GPUSize64 indirectOffset);

    undefined beginPipelineStatisticsQuery(GPUQuerySet querySet, GPUSize32 queryIndex);
    undefined endPipelineStatisticsQuery();

    undefined writeTimestamp(GPUQuerySet querySet, GPUSize32 queryIndex);

    undefined endPass();
};
GPUComputePassEncoder includes GPUObjectBase;
GPUComputePassEncoder includes GPUProgrammablePassEncoder;

GPUComputePassEncoder has the following internal slots:

[[pipeline]], of type GPUComputePipeline

The current GPUComputePipeline, initially null.

14.1.1. Creation

dictionary GPUComputePassDescriptor : GPUObjectDescriptorBase {
};

14.1.2. Dispatch

setPipeline(pipeline)

Sets the current GPUComputePipeline.

Called on: GPUComputePassEncoder this.

Arguments:

Arguments for the GPUComputePassEncoder.setPipeline(pipeline) method.
Parameter Type Nullable Optional Description
pipeline GPUComputePipeline The compute pipeline to use for subsequent dispatch commands.

Returns: undefined

Issue the following steps on the Device timeline of this.[[device]]:

  1. If any of the following conditions are unsatisfied, make this invalid and stop.

  2. Set this.[[pipeline]] to be pipeline.

dispatch(x, y, z)

Dispatch work to be performed with the current GPUComputePipeline. See § 21.2 Computing for the detailed specification.

Called on: GPUComputePassEncoder this.

Arguments:

Arguments for the GPUComputePassEncoder.dispatch(x, y, z) method.
Parameter Type Nullable Optional Description
x GPUSize32 X dimension of the grid of workgroups to dispatch.
y GPUSize32 Y dimension of the grid of workgroups to dispatch.
z GPUSize32 Z dimension of the grid of workgroups to dispatch.

Returns: undefined

Issue the following steps on the Device timeline of this.[[device]]:

  1. If any of the following conditions are unsatisfied, make this invalid and stop.

  2. Append a GPU command to this.[[command_encoder]].[[command_list]] that captures the GPUComputePassEncoder state of this as passState and, when executed, issues the following steps on the appropriate Queue timeline:

    1. Dispatch a grid of workgroups with dimensions [x, y, z] with passState.[[pipeline]] using passState.[[bind_groups]].

dispatchIndirect(indirectBuffer, indirectOffset)

Dispatch work to be performed with the current GPUComputePipeline using parameters read from a GPUBuffer. See § 21.2 Computing for the detailed specification.

The indirect dispatch parameters encoded in the buffer must be a tightly packed block of three 32-bit unsigned integer values (12 bytes total), given in the same order as the arguments for dispatch(). For example:

let dispatchIndirectParameters = new Uint32Array(3);
dispatchIndirectParameters[0] = x;
dispatchIndirectParameters[1] = y;
dispatchIndirectParameters[2] = z;
Called on: GPUComputePassEncoder this.

Arguments:

Arguments for the GPUComputePassEncoder.dispatchIndirect(indirectBuffer, indirectOffset) method.
Parameter Type Nullable Optional Description
indirectBuffer GPUBuffer Buffer containing the indirect dispatch parameters.
indirectOffset GPUSize64 Offset in bytes into indirectBuffer where the dispatch data begins.

Returns: undefined

Issue the following steps on the Device timeline of this.[[device]]:

  1. If any of the following conditions are unsatisfied, make this invalid and stop.

  2. Add indirectBuffer to the usage scope as INDIRECT.

add some validation related to maxComputeWorkgroupsPerDimension.

14.1.3. Queries

beginPipelineStatisticsQuery(querySet, queryIndex)
Called on: GPUComputePassEncoder this.

Arguments:

Arguments for the GPUComputePassEncoder.beginPipelineStatisticsQuery(querySet, queryIndex) method.
Parameter Type Nullable Optional Description
querySet GPUQuerySet
queryIndex GPUSize32

Returns: undefined

  1. If this.[[device]].[[features]] does not contain "pipeline-statistics-query", throw a TypeError.

Describe beginPipelineStatisticsQuery() algorithm steps.

endPipelineStatisticsQuery()
Called on: GPUComputePassEncoder this.

Returns: undefined

  1. If this.[[device]].[[features]] does not contain "pipeline-statistics-query", throw a TypeError.

Describe endPipelineStatisticsQuery() algorithm steps.

writeTimestamp(querySet, queryIndex)

Writes a timestamp value into querySet when all previous commands have completed executing.

Called on: GPUComputePassEncoder this.

Arguments: